You would certainly have some sort of ROI, and I’d imagine it would be quite good. It’s a reasonably straight forward calc actually. How much electricity do you use (in kWh, you’ll find it on your bill) and what % do you use during daylight hours approx. And how much do you pay per kWh (also on the bill).
I would have thought at that price your payback would be 3-5 years, and then it’s all cream. However, we generally recommend investing a bit more, at least in your inverter, which may put your payback period out further, but would also improve your chances in having a healthy system for longer (and improving your ROI in the long run).