use [ and ] in place of ( and )
(roll)1d100(/roll)
[roll0]
(roll=whatever you want to put here)1d100(/roll)
[roll1]
I don't think you can put multiple rolls in on command. I think you have to do each one separate.
I have not tried anything like 4d6, best 3, so I am not sure if that one works.
there seems to be a problem with too many rolls on one post, and once you post, you cannot add rolls. it requires a new post.