How active is your PT? If (s)he is also an athlete or works with many, then I would follow the recommendations. If not, then get a sport-experienced second opinion.
As far as roller skiing goes, it’s a great tool for ski-specific training. BUT. They take a lot of getting used to. And they have no brakes…
The first season I had some, I was nervous enough that I barely used them. The second season was much better and they were a great addition to my program. I would use a vehicle and several bikes to do uphill laps. Lock bikes at the top, drive down, ski up, bike down, repeat. (“Real” roller skis would just turnaround and go down, but wiping out on pavement sucks.)