Painting walls in my house?

Obviously not many people here have actually painted a wall or anything else with rollers. You should cut in your edges of a wall or part wall depending on the size you are working with and be sure to feather softly down so as not to create a line in your paint...then apply paint to roller. The point of using a roller is to save time, energy and brush lines on your wall. Run the roller up and down the wall in a sort of W type of shape moving up and down. Applying too much paint or (uneven) pressure will cause lines in your paint. Paint will tend to build up on the edges of some rollers, so one must ensure to squish off the extra paint on the edges of the roller.

From experience & 2 classes-don't do it randomly! AND you should stick with one direction ONLY!

-either roll all strokes up OR down, but not both. That's because the nap on the roller cover is different when you use it "both" ways(back & forth, up & down) - lines can appear AND remain when it dries. (You CAN do it horizontally, but again, only one way, like left to right, left to right). And maybe most important, when the roller, paint, & wall become "noisy", it means less paint is on the cover and then you need to put more on it. These areas can dry looking like they need another coat and can appear less smooth! And I hope you know to "cut in" (with a brush made for the kind of paint you're using) before starting rolling the paint on.

Not 100% about this, But I think you paint in relitivly straight lines but I dont think going off track a half a metre would ruin the wall. Hope this helped :)

You should do it in one direction, don't do it randomly, and apply two coats of paint, after the first one dries.