i don't think rotors were the wrong choice....not my choice in your situation but not wrong. Their placement was wrong UNLESS*** did you opt for one zone to save the 300 extra for planters?
And because of that, did the contractor say "then how will plants get watered" and did you say "overspray should be fine!".
If that is the scenario or close to it...then the contractors only mistake was refusing to do something he knew wasn't the right way to do it. If I were the contractor I probably would have told you the grass area is important and so are the beds..they should have their own systems. If you refused...I would have refused to do the grass in a way that would have compromised its coverage.
Move the rotors to the corners and use the proper nozzle...don't know RB5000s sorry can't advise on the nozzle. Then install new zone for planters.
Sprinkler Solutions, Inc.
Arizona and Colorado
www.sprinklersolutions.net