A SU-22 would have be parked on the ground at a distance of not more than 500mtrs. To be really effective the RPG has to be closer than that. Firing at moving aircraft could be done as a joke though!
The RPG is an anti-tank/anti personell weapon and to kill a tank it still has to fired at a close range. Now if they had a few Bofors with the required trained crew they could whang off 50-60 rounds a minute, with its very high muzzle velocity - who knows? However, the Libyan gunners etc., are all seemingly untrained rebels - indeed a rabble. But I'll give them 10/10 for guts.