Frater Rosae Crucis, abbreviated to F.R.C., is a title that the Ancient Mystical Order Rosæ Crucis (AMORC), a Rosicrucian organization, "awards" to its advanced members.
AMORC awards the title to those initiated into the 10th Degree of the order, these are members it considers to be at the master level of understanding of their teachings; generally acquired through many years of study of their material.
The use of F.R.C. after an individuals name mimics the addition of M.A. or Ph.D. to the names of individuals who have successfully completed their study in graduate school.
References
Frater Rosae Crucis Wikipedia(Text) CC BY-SA