Koopa Troopa acts as their leader, bold in their craft. He's a shapeshifter, and can turn others into Koopa Troopas, using it as conversion for his forces.
Koopa Paratroopa acts as the scout, having the ability to fly, cautious as ever. He has super strength.
Dry Bones acts as the enforcer, being the stubborn tough guy. He never dies, always putting himself back together. He speaks with "Kraggh"s. He can change his size.
Paper Troopa is a Koopa made of paper. He fits in tight spaces quite well.