How do you coat perfectly round truffles with melted chocolate?
I don't know about perfectly round, but you can do better.

Stick toothpicks in the truffles before dipping. Dip them using the toothpick, let it drip enough to make sure there's not a ton of excess, probably while spinning it a bit to let it cool slightly and make sure it doesn't all accumulate in one place. Then stab the other end of the toothpick into something to hold it with the truffle at the top. (A block of foam works, as does cardboard, though you might need to pre-poke holes.) 

This avoids having a lot of excess coating chocolate, which it looks like you're getting a lot of when scooping out with a spoon. There can still be a little excess, but it'll drip down the toothpick, not get smeared all over. It also avoids having to mess up any of the surface by touching it with the spoon.

Beyond that, they'll be as perfectly round as you managed to roll the centers, which is mostly just a matter of a bit of practice and obsessiveness. So they won't be perfectly round, but they'll be a lot smoother and rounder, definitely enough to impress people. You do get a small hole on one side of the truffle, possibly with a tiny bit of excess chocolate around it where it collected against the toothpick, but I don't think that's terribly ugly. Plus as long as a decent fraction are pretty, you can just eat your mistakes.

Here's what a friend and I managed on our first try:



As you can see, they're definitely not perfect. But we got better at it as we went along. A lot of the irregularities are from initial inexperience, variation in chocolate temperature (we didn't have a great water bath or hot plate setup), and simply not having terribly round centers.

Finally, you might want to practice tempering the chocolate a bit better. Having nice glossy smooth surface makes them look a lot cleaner even if they aren't perfect.