Unintentional textured pattern left in the paint by the roller. You wall may look something like this:


How Can I Prevent Roller Marks
There are many ways to prevent roller marks. Here are a few suggestions:- Use the proper roller cover - avoid too long a nap for the paint and the substrate.
- Use a quality roller to ensure adequate film thickness and uniformity.
- High-quality paints tend to roll on more evenly due to their higher solids content and leveling properties.
- Pre-dampen roller covers used with latex paint; shake out excess water.
- Don't let paint build up on the roller end.
- Avoid overspreading or trying to stretch the paint too far with every roller load.
- Begin rolling at a corner near the ceiling and work down the wall in three-foot square sections. Spread the paint in a zigzag "M" or "W" pattern, beginning with an upward stroke to minimize spatter. Then, without lifting the roller from the surface, fill in the zigzag pattern with even, parallel strokes.
- After rolling a 4" by 8' section (about the size of a wall panel), gently roll the roller down the wall, starting on the right and moving to your left. This removes any blobs or marks and takes care of any uneven application.