We wanted to raise our Friheten couch from Ikea so our roomba could fit under it. Raising the main part of the couch was easy simply purchasing legs from amazon and screwing the, in where the other legs attach. We bought these:

https://www.amazon.com/GLTECK-Tapered-Replacement-...

But the challenge became how to raise the pull out part of the couch.

With these legs, we found we needed 4" of additional height from the bottom of the couch frame. I was unable to find thin casters that were that tall that attached with only 2 screws, so I resorted to building up additional frame and adding casters.

Supplies

4 - 2 inch caster wheels from Home Depot. These were 2.5” tall.

2 - boards of 5/8” X 2.5” X 51 3/4”

2 - boards of 5/8” X 2.5” X 15 1/4”

24 screws of about 1.25”

Step 1: Attach Long Cross Boards

You’ll want to drill starter holes into the couch and your planks where you will attach them to the existing frame of the couch. This will help prevent the wood from splitting.

Align the long boards across the long edge of the couch. These will go from one side of the existing frame to the other. Make sure that they are positioned so that the won't block the movement of the hinges. I found this to be about 3 1/4" away from the existing wheels near the locking piece (the back) and right next to the edge of the front wheels, about 10 1/4" away from each other.

I recommend placing the boards where you think they should be with the couch top face down, and then raising the bottom of the couch to simulate raising the top. This will allow you to make sure the movement isn't blocked.

Once you have the boards in place, use a drill bit to drill through the long planks and into the existing frame of the couch. 2 screws on each end should be fine.

Once you have drilled the holes, you can attach the boards to the frame with screws. Use a drill on a low torque setting or hand tighten the screws.

Step 2: Align Short Boards

Next to get the right height, you will want to add one more board that connects the two long boards you just installed.

Again, position the short boards so that they will not interfere with the movement of the hinges. I found this to be about 1 7/8" from the outside edge of the frame. You want to keep them as close to the original frame as possible to maximize weight support.

Position the casters such that all holes will go through both the long board and the short board, mark, and drill through both boards.

Install casters and short boards using 4 screws per caster

Step 3: Adjust Lock Bars

With this setup and on a carpeted floor, I found the lock bars to be just off. I adjusted them and moved the angle such that the bar was closer to the ground when the couch is sitting on the wheels. You will likely have to check the amount to move it.

Step 4: Finish

When this was done, our Roomba was able to "almost" fit under the pull out part of the couch, but the newly installed cross bars were juuuust to short and prevented it from going under. So depending upon what vacuum you have or the thickness of your carpet, YMMV.