Given an Android phone, how can I find out what custom and stock ROMs are compatible?
This site offers a fairly comprehensive coverage to the questions asked by you:


Where can I find stock or custom ROMs for my Android device?
How do I root my Android device?
How do I update Android on my device?


Coming to your device in particular, it appears there is lack of developer support to create custom ROMs as a quick search (not comprehensive ) did not provide any evidence. Even the OEM, it looks like has not come out with any plans to update to Lollipop, whereas most popular phones have the next version Marshmallow rolled out or in the process of rolling out.

Possible reasons for lack of developer support, in general, could be (i am not a developer, so guessing):


Chipset being not developer friendly
Not a popular phone compared to low cost "budget phones"
Kernel and chip set information not "open source"
Difficulty in porting custom ROM from another ROM
OEM not coming up with a improved versions of phone