[Q] Superuser not installing topic

I have one problem. When I try to install new ROM, the recovery (TWRP) says that my device isn't rooted (I tried it on few ROMs, always the same...). Also, in the things that are shown when the ROM is installing (like mounting data, system, installing system files etc.) ins't installing superuser (I think that should be there)
Is there somebody to help me? :) Thank you...