This is one of those questions which do not have a clear written reply. Although it is known that one can convert an RTR to an FRTOL, the process is not known to me.
You might not have to write the FRTOL Exam, but I think you will need a SPL before you can apply for the license.
So, First SPL, then Application (along with current medical assessment) for the Issue of License. But here's the trouble, DGCA website has only one for concerning the FRTOL restricted. And that is for the Examination.
Try talking to a Flying School, or Even better visit the open house.
Post your experience.
All the Best.
Silent.