hi
The RocGen Plus documentation says that it will operate without a stable incoming video signal by generating its own sync. Without a stable incoming video signal would some genlocks prevent an Amiga from boring ?
Amiga genlocks may be very tricky sometimes (different behaviours with different Amiga models) and yes they can prevent your system booting.
Are you sure that your A1200 and your genlock are of the same video standard? both PAL or NTSC?