My current standard team makeup is:
2 Support(Laser Rifle, Laser Pistol, Skeleton Suit, Medkit)
2 Assault (Laser Rifle, Laser Pistol, (Arcthrower if I need live capture, else SCOPE), Skeleton Suit)
1 Heavy (Heavy Laser, Rocket Launcher, Grenade, Skeleton Suit)
1 Sniper (Laser Sniper Rifle, Laser Pistol, SCOPE, Skeleton Suit)
Why skeleton suits? Because its all I have researched at the moment. If I don't have an experienced soldier of one of those roles, I sub in a rookie with the same equipment (where possible, you obviously can't give sniper rifles/heavy lasers to rookies).
The rookies actually get the best weapons for me, because I don't want to research the extra laser weapons (figure I'll just jump on over to plasma) and the vast majority of my team can't use assault rifles. I have one assault, one support, a bunch of snipers, and a few heavies. So really, rookies are a valuable asset.
I think this might be a mistake. You seem to be able to get the laser research out of the way pretty fast (not sure if my Europe start boosted research, or just lab costs), and the weapons are a good upgrade, with a flat +2 damage bonus (+1 for pistols). I skipped laser pistols, and eventually gave my snipers the plasma pistols for backup.
My first live capture was a sectoid so I got the 50% research credit for beam research. This made lasers incredibly fast to research, and I already have all of my interceptors equipped with laser cannons.