So this is my first jam and I wish to know by prior experience if it's best to go solo or with a team. Also what team size is usually good enough and what roles each member should have. Is there any need for all members to know how to program?

If you go with working in teams not every member needs to know how to do a task, in fact that may get in the way. If you construct a team of many people with the same skills, you may find that people moving between different tasks can interfere with other peoples work on those tasks and make it harder to organize. That's not to say it's not possible, it is, but from what I've seen teams usually seem to form more organically around members with more specialized roles, even if people share similar skills they tend to settle into one or a handful of them for the jam.

There's no simple answer for whether Solo vs. Team is better, there are upsides and downsides to both. In solo work you have complete creative control. In teams you have more people so you can often achieve a game of similar quality but larger scope, or same scope and better quality, without as much stress or load, if everyone's working well. Plus in teams there are other people to bounce ideas off of. However you should make sure you work well with the people you'd be teaming up with, negative interactions with team members could be detrimental.