Can't find information about a family name that I'm descended from?

From word of mouth, and very little written account I learned that I'm descended from a (at the time) well known family (clan) of gaelic druids of the surname Roshel or Roshael. I've googled, with no legitimate results. I've asked family, but the knowledge has deteriorated over the time and the fact that many generations since have been Christian. I want to get back in touch with my roots and ancestry and faith. If someone knows anything, or where I can find the information that I am looking for I would be extremely grateful. (I only ume someone would know because, like I said, at the time they were a well known and respected family)