I don't think that I have yet sorted out Roland lines. What should I do to have an idea of what I am looking for?
The blunt answer would be: "Go to www.roland.com". 😀
But more seriously their "lines" are something like:
- FP: portable pianos with speakers, they vary from low-end to high-end and cheap to expensive. Currently the high-end FP-90 doesn't have Roland's latest and greatest tech, but that's because it's been out for a while already. The FP-10/30 are quite low-end (for Roland) but competitive with the cheap models from Yamaha/Kawai/Casio for example. FP-60 is somewhere in the middle.
- RP: cabinet digital pianos with quite low-end tech (again for Roland, but still perfectly modern tech) and moderate prices, An RP-501R for example has similar tech as the FP-30 plus some extra features.
- F: compact models, otherwise similar to RP, so an F-140R is pretty much the same as an RP-501R.
- DP: compact models with higher end tech. But the DP-603 has been out for a while now, so it doesn't have the absolutely latest and greatest that Roland has to offer. Not cheap.
- HP: mid and high range models in fancy cabinets.
- LX: premium models with elaborate speaker systems and fancy cabinets
- RD: stage pianos, mostly without speakers the RD-88 being an exception
- Kiyola: A "designer piano" with quite high end tech.
Something in the HP line would be the most likely competitors for e.g. a Yamaha CLP-745.