About a year ago, I put new tires on my truck. Now I'm hearing a lot of road noise. How can you tell the difference between tire noise or wheel bearing noise?

Tires just don't start making noise if properly maintained. If you're uncertain where the trouble is, just calculate which choice costs more, that'll be the one.

Have your tires rotated and listen to what the noise does.

edited to add: If the noise doesn't change/stop it's probably not the tires.

Tires won't just do it in a day, but they can get noisier over time, like the Falken's on my 250. Horrid tire.

Try this:

As you're going down the road and you hear the noise, try to maintain that speed until you go through some sweeping turns. If you've got a wheel bearing on it's way out, it should get noticeably louder on the side that's taking force in a turn.

Left turn noise -> Right WB
Right turn noise -> Left WB

Further check:

Jack up one side front tire. Grab it at the top and bottom, and push/pull. Try and rock it back and forth. If you've got any play in the wheel, you've found your culprit.

Easiest check:

If it's a GM truck with 60k or more miles, it's the wheel bearing.

ok try this. Get it up on two wheels you might need a ramp and make sure you drive slow on two wheels you don't want to tip it over. which ever side you here the noise on that's the one you will need to fix

Some tires make more road noise than others do. And tread pattern has a lot to do with it. More aggressive tread (mud tires) is noisier than road tread. Were the new tires the same make and tread as the old tires?

I don't know what kind of truck it is, is it 4x4 or 2wd?

For trailer axle bearings and front bearings on a 2wd jack up the tire of the bearing in question and spin it as fast as you can by hand, then put your head close to the hub and listen. If there is a growl sound or a siclical click clung or grind you have bearing problems.