Could you tell more when you mean this?
Sorry for not expanding the abbreviations
MOUT = Military ops in urban terrain.
FIBUA = Fighting in built up areas.
RPG detachments on roof tops can target the top of all armd vehicles in ambushes. The top of the armd vehicle has the weakest armour protection, so an M1/ Merkava are as good as a T-55/ T-72 in a built up area.
In conventional ops the defender has to face the front of the tank (the strongest area), and the RPG-7 just does not have the punch required to knock out a tank from the front, it can at best attempt to disable it by hitting the tracks, and that is at 500 mtrs.
At 500 mtrs, the poor sight system of the RPG launcher is not very accurate, coupled with the enemy arty barage and smoke, making aiming a very difficult task. If by that time the enemy tanks are 300 mtrs away, and have not been stopped, then nothing else will.
The accompaning infantry with the tanks does not allow RPG detachments to out flank the armour close enough to do any damage.