how many different derpling rolls are there and what are they (if to many just tell the coolest/most important ones)
The few you have most likely seen before are:
Assessors: The ones who weaken themselves and go without cybernetic enhancements in order to gather data more purely.
Scouts: The ones who sacrifice their strength and size for stealth, currently they monitor the situation in the domain of the Pigrons.
Ambassadors: You haven't met these, but the crimson has and completely mutated them.
Some of the more important ones are:
Researchers: Which take the data collected by lower roles and/or gather it and convert it into either applicable knowledge or inventions
Guardians: Which make sure no unauthorized entities enter the dimensions exclusively occupied by derplings, they have the most powerful weapons out of all roles.
Managers: Which manage all other lower roles.
Keeper Of Knowledge: There's only one, and I fill this role. My task it to give knowledge to derplings (and some others, of course
) who request it and compile all research into one place.
There are many other roles that I did not mention.
do you ever make allies with entities in other dimensional clusters, such as terrarians or foragers, or do you avoid messing with them
We have not, we tend to observe other dimensional clusters rather than intervene with them in order to preserve their purity.