I roolerblade, skate board, and ride a road bike in the effort to keep active and in some shape for skiing. If you need to split hairs on what's best for what, that's all fine, but my program is pretty much dictated by my kids preferred activity at that moment, and make the best of it I can.
My thoughts given my tools, road biking for strength and endurance, skate boarding for stance and road feel, and roller blading for fine foot muscle control. When much younger, I used to roller skate and ice skate and think it might be better for the fine foot muscle balance, but I use what I've got.
But my ski goal is pretty much survive/enjoy the groomers, find more efficient ways down the hill, and don't yet explore anything too tough (for my skill set). So, its likely, your goals might be higher than mine.
Good luck finding your answer.