Patchy result after 2 coats

I started decorating my house and after the second coat of trade matt emulsion the paint on the walls looks very patchy.
The house is only 6 years old so before I started decorating I lightly sanded the walls down and then washed all walls with a sugar soap solution.
I am using a roller with hamilton perfection medium pile roller sleeves and no nonsense trade matt emulsion (not diluted with water).
After examining the patches that appear to be rough I noticed that if I place a flat object against the wall (e.g. a ruler) I can see that the wall is not perfectly straight. There are parts that are slightly dented and uneven by 1 or 2 millimetres across a couple of inches. It appears that the roller sleeve doesn't come in close contact with those parts of the wall and the paint looks patchy and not smooth.
As this is the first time I decided to decorate a house I'm not an expert by any means but read a lot online before starting to do the work. I need some recommendations as to how can this be remedied.

Think you have answered your own problem, the roller is not making full contact with the wall,
Being a Decorator (Old School) I very seldom use rollers, still stick to a 6" Emulsion Brush,( it gets into places a roller cant )

Yes. Or use a 4" roller on the uneven parts of the wall.

It's a 3 story house and it feels like it will take forever if I have to use a brush instead of a roller!
Is using a brush going to make it look any different though? I thought the solution would be to either sand down the area around the dent or something else that I don't know as I've never painted before.

More likely to be application technique,First thing with trade paint is it needs to be thinned about 10% usually.make sure you load the roller even and roll in all directions,Are you using a pole on the end of the roller as this will help with the correct pressure on the roller

I didn't thin down the paint. I don't think I rolled the paint towards all directions either as the roller was on a pole and found it difficult to roll towards all directions. The result is really ugly! From a close look the surface of the walls look like the surface of the moon! Loads of patches of many tiny craters. Like the close up image below. Any suggestions as to what I can do to put it right?