[Rails] Roll my own Role based permission or use CanCan Gem?

I'm fairly new to the Rails community and recently faced a similar
situation. First from what you describe, CanCan will most certainly
provide the functionality you desire.

Secondly, there is a nice screencast at Railscasts.com that provides a good
introduction, however some of processes in the screencast have been
updated/modified in more recent versions of the gem, so be sure to go by
the github documentation vs. the example in the screencast.

Thirdly, I would describe the learning curve for the CanCan gem as
moderate. I have a fairly complex use case and my CanCan Abilities class
has gotten a little large. However, I've been amazed that each time I
initially thought CanCan was in error, when I worked it through, CanCan was
accurate. Also, I was worried about a performance hit, but so far have not
seen anything that indicates CanCan will not scale.

Highly recommended gem from my standpoint.