Has anyone used to this OS to build android Roms or Kernels.
Well, it is just GNU/Linux. If you know how to build them on Debian/Ubuntu, they’ll work fine in Ubuntu MATE too. Other distros will as well, providing the instructions are adapted as this distro is based on Ubuntu.
I haven’t built ROMs or kernels myself, but I have compiled other kinds of software. 
Also, welcome to the community!