My DH just put one together. The body came as one piece. The handles and the legs with wheels came separate. Look at the legs and see if there is a black ring or a place where the wheel section goes into the upper part of the leg. If so, you should be able to separate the two pieces. See if the handles can come off. This is were height is adjusted on the one we have so should come out if urs is the same. Because of the break lines, you will need to be able to remove both handles and wheels. If you can, just switch them around.
If not like mine, the wheels should be able to be removed. You need to be able to replace them when they wear down. Look to see how they are screwed onto the leg. It may just be a matter of removing the wheel, switching it to the inside and screwing it back on.
I suppose any handyman could probably figure out a way to jury rig the wheels but I wonder how helpful changing the wheels really is - on both our walker and rollator the wheels don't extend much beyond the width of the handles, and the user has to be able to hold on without scraping their knuckles. And I wonder if it would it make the rollator less stable?
If not like mine, the wheels should be able to be removed. You need to be able to replace them when they wear down. Look to see how they are screwed onto the leg. It may just be a matter of removing the wheel, switching it to the inside and screwing it back on.