Is this the right emulsion roller

Hi, Ive emulsioned a couple of rooms recently, new plaster, thinned paint by 20%, used Leyland trade mat emulsion, and Dulux medium pile synthetic roller which says its for smooth surfaces. Every thing looked good until this morning when the sun was shining through the window. It shows that the emulsioned walls have a rough textured finish. Ive never notice this on previously painted walls and was wondering if it is the paint, the roller or if i have thinned it incorrectly. I have only applied one coat.
Any advice welcome,
thanks Phil

What is the Exact wording of the make of emulsion ? and instructions ?

Also, you have only first/mist coated your walls, so they will not look great with only one coat.

Yeh..if its the first coat it tends to soak in very quickly, not giving the paint time to flow out..give the wall a nice rub down with 100 grade abrasive paper..the green stuff.

And wrap it arounf a wooden bloc...saves your fingers and you get a better finish.

Its Leyland Trade Contract emulsion and it actually say's to thin by 10% on porous surfaces. So maybe I have thinned it a little too much. Anyway, I've given the walls a light rub-down and used a short pile roller and the result is very nice so was it the roller or the mix ratio