So apart from the uneven edges, in my opinion (but I am just an amateur myself) a long-pile roller was used here. This results in this coarse texture. For a finer finish, a short-pile roller should have been used accordingly.
Unfortunately, pure amateur opinion. A buddy of mine is a painter and at the end gave me the "fluffier" roller for trimming because it allows you to get better into the corners. The result was identical to the short-pile roller. We also did the surface with both roller types. No difference. For the colorful walls, we only used the long-pile rollers sold in hardware stores for "rough walls." My walls, however, are sanded and filler-coated Q2, ceilings fully puttied. My guess, but also as an amateur. The painter skipped the second coat or the "smoothing" and just slathered on thick paint. That works with textured wallpaper, you don’t have to coat the whole house twice. With a smooth wall, this went wrong. And sticking a fleece wallpaper edge to edge without seeing a seam—I already managed that as an amateur in my rental flat 15 years ago...