Roughly 1k for the 23 degree rockets, and 2.2k for the 45 degree rockets.
If your moving of course that changes things. As does changes in elevations or shooting from unlevel ground.
From the testing I did a rocket killed building on impact 3 out of 4 times. This is assuming a direct hit, not a slightly off target hit.
(Blast damage)
You can bring vehicle supplys with you, that will let your reload your rockets 4 times.

The 23 degree rockets "Can" leave you in ack range at some locations before your hitting buildings.
So be careful.