I did my old mini with a roller. Came out okay, with a bit of the old orange peel effect, but atleast it was all one colour, and it made me 300 quid profit when a year later I came to sell my car.
I used rustoleum paint, and got it mixed (can't remember who by, by everybody on the mini forums who'd done it recommended them. They were awesome. Very friendly, cheap, and quick), to the old BMC Tartan red, it cost somewhere in the region of 25 quid for 3 tins I think and in the end I gave the mini 3 coats and still had a tin left over.
I used sponge rollers, but in hindsight im not sure if I would have used a synthetic roller instead as the orange peel mainly came (I think) from the fact I was essentially using a sponge (albeit a rolly one), to apply the paint.
Like I say the finish wasn't perfect, and I learnt the hard way that, after giving it it's final coat, wait more than 12 hours for it to cure, before bolting back on all the chrome bits, and bumpers etc. I was too eager, and it was my daily drive, so I gave it it's final coat about 8 or 9 in the evening, and the next day about 11 oclock in the morning I was back at the garage bolting everything back on. The paint was still a bit wet, and I only thought it would take half hour or so to put back the rear windows, boot lid, wipers, bumpers, lights, bonnet, grille, etc. In reality, I should have left it about three or four days, and then left a day to get everything back on.
Anyways, I'll find some pics of her before during and after and post them so you can see what kind of finish you'll get. If somebody like me (bullish and impatient) can do an okay job on my first go, I imagine most people would find this very easy and get superb results.
If I ever I decided a defender or series of mine needed a repaint then I wouldn't think twice about doing it this way. So cheap in comparrison with a proper respray, and on a landrover, gives just the finish you want. So as you're not too precious with it, and it looks rough and rugged, but presentable at the same time.
Anyways, I'll dig out those pics...