What kind of biking do you do? Sometimes it's not worth the hassle unless you're a die-hard rider. We started off carrying them and they got filthy and staying near the coasts they started rusting from the air. We decided we didn't use them enough to justify them. Do the types of places you like to stay have good, safe riding? We know a few folks who haul them around and never use them .... but they might. If you just do campground biking, walking might be more beneficial.
If your Class B doesn't already have a tire mount on the rear, you can get one that swings away in order to open the rear doors. Here is one but I'm sure there are others. Perhaps you can find a used one. Roof racks are expensive, also.
The free bus from Aspen runs 8:00am to 5:00pm only. Its the popular option with most short term visitors. No personal vehicles allowed on the road during bus hours.
I prefer to drive in, which means you have to enter before the start of buses at 8:00am and can't drive out until the buses stop at 5:00pm. It was s a $10 fee to drive to Maroon Lake parking lot last time I did it, but I heard it was being raised to $20
During the peak fall leaf season, last 2 weeks Sept & 1st week Oct, there are very large crowds and additional restrictions, During these weeks if you try to drive in, you'll end up in an overflow lot.
I'd recommend taking the bus. You can only drive in during certain hours and parking is very limited. Here's some good information.