There was only one rover engine I could not get running and it was a 1.6 IOE in my 51. Way too much rust in the cylinders.
If I were you, I would pull the plugs and dump a releasing agent (Marvel mystery oil, PB blaster, even ATF) put the plugs back in and let it sit for a week. If it won't turn, pull the head it will take all of an hour.
The killer is not the engine as you can get a running one for a few hundred dollars. The bulkhead and chassis are the issue. If they are ok, it is restorable. If not, they are expensive, but it is still restorable.
Pictures please.