Accidental marks and blobs and whatever are just a part of the painting process. Yes you can get tight, detailed and very controlled painting. But "freestyle painting" I guess it has been referred to today, means to me, free, loose, natural, organic, and barely controlled. I LOVE accidents! And you have to be totally OK with stuff going wrong. Just like raising a kid - this paint combo between tool and paint just has a mind of it's own. And your job is to roll with the unexpected and make that "accident" work for you.
The above images clearly show that as I was using a rubber patterned roller, because the paint's thickness is slippery, and the fact that the paper is not great for this kind of technique (really I should be doing this on fabric or the wall!), the roller literally slipped with the paint and smeared all over the place. The top image shows smearing top-left to the right-down areas. In this second image above, right in the middle you can see those flowers are not crisp at all! Totally smeared and blending into one another. But that's the beauty of it! It's not perfect. I'm not trying to render a beautiful pattern (although that is what these rubber rollers are meant to do of course). I love the "suggested" patterned effect. It also makes it visually more interesting, the eye is challenged and stimulated by the irregularities, and is surprised (perhaps annoyed but that is ok too) of the slight variations and always a joy to disrupt what is "expected" for the viewer. It also suggests some kind of worn, vintage look. Things eroding falling away, not perfect. 
This is even more obvious in the painting above. I did not "properly" even out the paint in the roller so it blobbed on in uneven marks. Super gloppy and then super faint. But still suggesting some kind of pattern and uniformity that I think is quite interesting.
And finally, the above image show that as I was completely running out of paint, rolling it over and over onto the canvas, the pattern completely disappeared leaving random, almost brush-like strokes reminiscent of a Gerald Richter painting abstract painting. An effect I totally couldn't have possibly come up with in my head! Proof you have to try and try and experiment. Roll with it. I'm never disappointed so you have to open your mind and let yourself turn those "mistakes" into those precious parts of the painting that is UNIQUE, special, one-of-a-kind, different, unexpected and beautiful.