I will try to address each of your questions in turn; hopefully that will make this answer clearer. I'll say upfront that I'm not going to list out EV spreads for each role the way you've requested -- the reason you can't find those is that they're too simple to be useful, and you'll see why that is as you read. Apologies in advance for the length of this!
Regarding roles in teams
Not every team needs to have the same number of Pokemon in the same defined roles. Different teambuilding 'archetypes' exist, which each invite you to use different combinations of roles to ultimately win a game. In this sense, your general 'game-plan' for each match can vary based on the Pokemon in your team and what they do. It's not always linear.
To understand roles, you need to understand their purpose in the context of a team. Generally, you will see advice given about teams that follow the 'balance' archetype. Balance teams work by building around a couple of sweepers (or otherwise, 'win conditions'), and enabling them to win the game. This is achieved by using 'wallbreakers', which are selected to compliment your win condition/s and counter a range of defensive Pokemon in the game. Balance teams also include utility Pokemon, 'pivots' and traditional walls which check offensive Pokemon, and give you ways to switch into and preserve your most damaging Pokemon.
However, balance is not the only team archetype that exists. Teambuilding is dynamic, and can involve many different strategies. Some metagames get completely broken by stall teams, which stack a bunch of tanky Pokemon on one team and win through self-sustain and countering set-ups. Some players like to use offence teams, which focus mainly on set-up sweepers and breakers.
These are very general examples of team archetypes. You can layer lots more complexity when trying to segregate team archtypes based on the roles used in them. (For example, 'bulky offence' plays more conversatively than plain offence, and 'semi-stall' teams pack an offensive edge.) All of this is to say that you should not confine yourself to always having a physical and special sweeper on your team with a physcial and speical wall. That's an easy way to start, but as you come to appreciate how competitive battles work, you'll find that teambuilding is more about planning a way to win than satisfying a team structure that is so regimented.
Which EVs for which role
The only strict rule here is that the EVs you use should compliment your Pokemon's role. This leaves things quite open to the imagination, which is probably why you're having trouble with this.
To make things simpler, I'll generalise with another rule (which you will eventually learn to break): usually, Pokemon should completely max one stat, and then spend a majority of their remaining EVs on a second stat. Frequently, that second stat should simply be maxed as well, producing the trusty 252 / 252 / 4 spread, which is ideal for many Pokemon, even at the highest level. That spread will never lead you too far astray, and is more than adequate as a starting point for all your movesets.
Though exceptions exist for everything, most roles have a clearly defined 'most important' stat. This stat is the first one you'll be looking to max, or at least make your most significant EV investment in. For offensive Pokemon -- attackers, sweepers, breakers, etc. -- this is almost always their preferred attacking stat. The second stat, receiving the next significant EV investment, is usually Speed (which, as above, is often maxed as well). However, some offensive Pokemon have very low Speed, which leaves an incentive to spend EVs on HP instead. Maybe they'll invest some HP and some Speed. Again, teambuilding is dynamic and rules exist to be broken.
Defensive Pokemon, including pivots and utlities, almost always max HP first. HP is the most important defensive stat, as it pays you back against both physcial and special attacks. However, as you've recognised, even defensive Pokemon tend to be biased toward either physical or special defence. Frequently, your second most significant EV investment will go to one of those stats. However, some support Pokemon prefer to use Speed to shut down faster threads, or an attacking stat to decrease their passivity. On some Pokemon, it's indeed viable to make sizeable investments in all of HP, Def and SpD. You will learn with time when it's appropriate to deviate from the norm.
How can you tell which stats are most important? It's a complex interplay of your Pokemon's base stats, its strengths and weaknesses, the needs of your team, and also the metagame overall. You can get it right 80% of the time by seeing, for example, your Pokemon's base Atk is better than its SpA so you should make it a physical attacker. Otherwise, it's simply something that comes with experience.
Spreading out EVs more
You would have noticed in the explanations I gave above that the second stat isn't always maxed out. This is where we begin to explore EV spreads with investments in a variety of stats, and EV spreads that spend considerably on three stats instead of two.
This is reasonably advanced teambuilding, and it's fine if you just want to ignore it for now. However, I will go over some of the reasons why you might take away EVs from your 'most important' stats to make small (or large!) investments elsewhere.
In competitive Pokemon, you not only worry about the types of Pokemon you'll face, but also the specific species. Particular Pokemon end up facing each other frequently, as players tend to switch counters into their opponent's Pokemon. You can prepare for these common matchups using clever EV investments.
This might be illustrated best with an example. Smogon's Heart Swap Magearna drops some of its trademark SpD to invest 28 Def instead. This looks benign, but it's calculated. As explained in the set details, those few Defence EVs take Magearna out of range for an OHKO from Landorus-T's Earthquake, and a 2HKO from Mega Medicham's HJK. This is quite a lot of value to get from so few EVs, and that is why people spread out EVs in strange ways. It secures small advantages in common matchups within the metagame you're playing.
Offensive Pokemon might do that same thing with their non-preferred offensive stat to let a surprise coverage attack secure a crucial 2HKO. Some Pokemon can invest just a few Speed EVs to outpace a threat; for example, Clefable only needs 12 Speed EVs to move before 0 Spe neutral Tyranitar, and smack it with Moonblast. When you start stacking these small optimisations onto each other, you can get some nasty looking EV spreads.
With time, you'll learn when it's worth making small tweaks like this, and even when it's worth making big tweaks, like investing 100 EVs to a third stat to end up with a spread like 252 / 156 / 100. Try experimenting with a damage calculator and seeing what you find. Are these absolutely essential? Definitely not, but when you see one of your optimisations come into play, it's extremely gratifying.
One other optimisation you might notice is people using 248 HP instead of 252. This is because it's better to have an odd amount of HP points, as Pokemon's damage calculator rounds down percentage-based damage. The game is full of small intricacies like this, and you needn't worry about them all now. The best thing for a beginner is to read moveset analyses (especially Smogon's) and practice playing matches. Even though these things aren't super easy to grasp at first, it all comes with time, experience and patience.
Let me know if any of this remains confusing and if you have any more questions about it!
