I enquired overnight from a friend who has competed in both figure skating and artistic roller, and has tried both quad and artistic inline wheels. Her report this morning, in brief:
Don't buy dedicated roller boots for inline. They are designed to be used with quad wheels. The roller boots are lighter and more flexible, too much so for inline wheels. Quad wheels are more stable and don't need as much support. You're safer using figure skate boots. Also, artistic inline frames come with either three or four wheels (rather like the difference between a 7' or 8' rocker on blades only you feel more of a difference in the balance on wheels), plus a toe wheel used for jumps. You need a coach to advise you which you need.
She doesn't advise using artistic inline frames for a beginner who is also a beginner level on ice. Learning the same moves (edges, turns, stops, etc) on inlines is quite different and more difficult than doing them on blades. It's not a simple transfer of the same movements from blades to wheels. The learning curve on inlines is much steeper and more suited for an advanced level figure skater if you're moving from ice to floor. (She learned roller first and later moved to the ice, which is an easier switch, she says.) If you really have your heart set on learning both, then think of them as two different sports and be prepared for the headache (literally) of having to concentrate and remember the differences in technique moving from blades to wheels and back. Wear a lot of safety equipment as inevitably your concentration will slip and just a second's error can result in a nasty fall, especially on the inline wheels. The heavy concentration will preclude skating with friends for enjoyment. You need no distractions, and preferably an inline coach standing by.
Speaking for myself, I adapted to quad wheels fairly quickly, although spins took a while to learn, but I had competed on ice at the senior pair level nationally, and am still at a fairly advanced technical level. On the ice I use Risport RF1 boots, and Riedell Bronze Star boots with my quad wheels on the wood floor of our club's wheeled-sports gym. I checked the details on the boxes my wheels come in, and I use Roll Line Giotto Freestyle wheels in the 57 mm size, 96A hardness. I don't know anything about choices for inline wheels.
In order to advise you better about boots, we need to know your foot shape all over, not just that you take a C width in your Risports. It's pretty much impossible to accurately measure your own feet. If there's no good skate shop near you with a professional fitter, at least have someone else measure your length, width at various points, standing and sitting, and describe your arch height. What shape are your toes -- Egyptian, Greek, etc?
My friend really advises learning artistic roller on quads instead of inline wheels if you're at the beginner level on ice. Much safer. Either way, please don't attempt the skating elements you've already learned on the ice on wheels of either kind without a coach. The technique is quite different. If you wanted to skate with friends outdoors, then she says to buy a rollerblading skate set that fit you and just enjoy cruising along, but don't try figure skating moves in them.
Good luck!