There probably are several for various lines of Carroll. However, only the specific family line that the herald has created the coat of arms for is entitled to use it. In some cases the CoA may only be used by one person. There are companies that claim to be able to find your family coat of arms, and what they find may well have been used by a member of the Carroll family. But that doesn't mean that it is legitimate for you.
This article may be helpful: http://en.wikipedia.org/wiki/Coat_of_arms