For one thing, James wants to legitimately win the tournament in the episode.
Personally, this is how I view Team Rocket in most of the normal episodes.
James - Semi-Innocent bystander that gets roped into just about everything after Season 1. He basically follows along with Jessie because he feels he has nowhere else to go.
Meowth - The go-to guy who acts like he 'has all the answers'. He is always identified by the overly dramatic past.
Jessie - A manipulative controlling antagonist who ALWAYS has to have things her way. When she doesn't, she either throws a fit, or does the 'poor me' routine.
A few of the 'very special' episodes (such as the one where James goes back to see his rich family) often show temporary changes in their characters. These are exceptions to the rule. Of course, after those it's business as usual again.
As far as whether they're evil or not, they really aren't. I mean, they're basically Ed, Edd, and Eddie's Japanese counterparts. They're not really bad or anything, they're just not very bright.