[ammoniadog]

These are pretty basic questions you are asking.

No, you don't need to stick with rotolocks. I hate rotolocks and get rid of them any chance I get. I never understood what the point of them was, especially if you still have a sweat-in filter drier that still requires you to lug your torch out for. It usually just means more tools for me to drag around in order to do the job (pipe wrenches) and more cussing while I try to get the rotolock undone without twisting the discharge line around like a tootsie-roll. I like brazing. Brazing is good, rotolocks is bad.

Yes, you should be able to legally install a phase monitor without an electrician's blessing. The electrician has jurisdiction UP TO the disconnect switch. Anything after that you should be able to do whatever you want. In many areas it's even common for the HVAC/R tech to deal everything starting at the breaker, including the disconnect.

If you don't want to deal with installing a phase monitor, another option would be to swap out the contactor with one that has overloads and a manual reset (starter). That way if the building drops a phase, the amps will go up and the starter will trip. I'm not really sure which would be easier or cheaper to install, just thought I'd throw the option out there for ya.