UHF Transmitter - Arduino - How to
Estimate the bit rate required.  Then choose a modulation method and estimate the bandwidth required for the bit rate.  Then search your local radiofrequency allocations for suitable spectrum, according to how much you can pay.

Or, as you suggest, begin with a radio module and work backwards.

A 433 MHz ASK UHF radio module (various vendors) can possibly get you around 10 kilobits per second, so as long as your video frames can fit into 10 kilobits you will be able to do it.  But 10 kilobits isn't much of a picture.