Attemping to paint a textured wall..?

Ok, my living room walls were horribly done from someone before me. it looks like they slapped mudd on them and never smoothed it out. It's bad but theres something I can do about it. I'm going to paint but not sure if a big thick roller would work or be more trouble. I'm thinking I"ll have to do it all by hand with a paint brush. Any tips that would make my painting experiance better?