You could probably put all the roles into an array:
example = ["role1", "role 2", "Another Role"]
then use the random utility to select one.
from evennia.utils import random
selectedrole = random.choice (example)
as for the cmds. Are they always the same for every round but different for each role or is each round going to be different regardless of the role the player plays?
If it's the first, you can probably type the cmds to a typeclass that re-presents the role and assign the typeclass dynamically to the character object once a role is assigned.
If it's the latter, someone else should probably take to answering that one. I'm still pretty new myself.