Hi Rehan
Please try to go into SU01 and see if you can remove the single role yourself. You will notice that it is in blue as it's indirectly assigned due to the composite role. Try to delete it and see what result you get.
Next up, what sort of cleanups in PFCG and PFUD can you see that might assist you?
I recommend you brush you up on your basis security transactions 
Regards
Colleen