Some people prefer stands and other types of trainers over rollers, but to me there are a few appealing aspects of rollers vs others:
Faster / more intense Workouts
More challenging / engaging
Better all-over body workout
No adapting or installation - just set the bike on and go
Some may argue that it isn't worth the cost (a new set can be bought ~ $200) and time to build your own, but that can be said about almost anything-
I enjoy building things, I had all the materials that I needed, and it only took a weekend to build.
The building isn't particularly challenging, so long as you are familiar with basic construction / projecting techniques, and have access to the necessary tools and materials.
I would not however suggest this as a first project, or for someone who does not have experience with similar projects.
P.S. I do not intended for this to be a set of step-by-step construction plans, as I feel that those who will likely have success in completing a project like this will be able to easily fill-in the b_a_ks that I may leave.
P.P.S. This is another homebuilt setup (much more sophisticated than mine) that I didn't find until writing this - however for me the free-motion feature isn't very important :
Step 1: Parts and Materials
I know that there are improvements and tweaks that others will find as they build their own which will result in better and diverse versions.
Some material suggestions:
3" PVC pipe 3pcs @ 18"
8ft of low stretch webbing - or tubing, rope etc
6+ Ball Bearings
Steel Rod 3pcs @ 21"
Dimensional Lumber - or other material for frame