Round is only good in doubles and triples
1 pokemon that uses round : 60 base power
2 pokemon that use round : 120 base power
3 pokemon that use round : 180 base power
STAB affects but it's for only the pokemon that uses it
Although each Pokemon on your team attacks, the actual power and effects of each hit are based on the original user only - any items held by your team do not affect the damage dealt.