When you are spinning, the unspun fiber can be matted in your hand if you are holding onto the roving too tightly. I tend to break my roving into shorter pieces so that if I do get too tight a grip, it won't have a chance to matt much roving.
I also treat the roving like a little bird or butterfly that I don't want to crush, so the fiber is just resting in my hand (in the crook of my pinky, actually...) and not being squeezed.
Also you could split the roving lengthwise into skinnier pieces -- some roving seems to want to split, which can cause segments to bunch up behind your hand while one segment alone gets drafted. That way, there's less width to draft across, too.
If the fiber started out matted, there are two things you can do to help unmatt it. First, break it into 1-2 foot lengths and "crack the whip" with each piece from each end -- the snapping tends to open up the end. Second, predraft the roving -- even if done just a little bit, this helps start the sliding process of drafting so that when you spin and draft, it drafts more easily.
A note when pre-drafting -- hold your hands 1.5 * the staple length (individual fiber length) apart for easier pre-drafting: if your hands aren't holding onto both ends of a single piece of fiber, then you won't be having your own personal tug-of-war.
For related entries, see:
Do you pre-draft your fiber before you spin?
How do you go from spinning fine to spinning thick?
Do you have a spinning or sock machine question for the belle? post it in a comment on the blog or contact me. Thanks!