Savage Worlds doesn't exactly define a standard party size. And, like most open-ended point-build systems, doesn't define "standard roles," either.
That said, the nominal limit seems implied by the bennies coin sets being about 50 coins... the expectation is that players start with 3, and earn up to 3 more, and the GM gets 1 per PC and 2 per wildcard character... for 7 per PC, plus 2 per wild card, and really, one wild card per PC sounds about right... so that puts 5 players at right about 45 in use.
Not that the system can't handle larger group sizes. It's just the bennie sets I've seen are all 50 tokens, and 50 tokens really only supports about 5 PC's.