With the exception of KSP Burst (regular and lite) causing the game to hang at "Loading Part Upgrades," and MechJeb2 Dev release and RSSVE giving the incompatible warning RO/RP-1 runs well on 1.12. Also RemoteTech gives the in-game warning that it can cause problems with Kerbalism.
I have to admit defeat and that I am wrong. RO/RP-1 does not work properly on 1.12. I continue to encounter the issue of being unable to leave a building once inside. I click the button to leave and then it disappears leaving me stuck. Also, I have not been able to enter the VAB/SPH.