Right, there are 2 ways to use rockruff, rocks suicide and choice band,
Suicide rocks
Rockruff @ Focus Sash
Ability: Steadfast
Level: 5
EVs: 4 HP / 252 Atk / 252 Spe
Jolly Nature
- Stealth Rock
- Stone Edge
- Crunch
- Fire Fang
This set is relatively easy to use, just set up rocks and sweep if you can.
Choice band
Rockruff @ Choice Band
Ability: Steadfast
Level: 5
EVs: 236 Atk / 36 Def / 196 SpD / 36 Spe
Adamant Nature
- Rock Slide
- Return
- Crunch
- Fire Fang
this set gives it enough bulk to live a hit from most non boosted Pokemon in little cup and it still outspeeds most mons in the tier.