So if you look at the attached image, you should be able to get an idea of what I'm doing. I want the text and its shadows to appear like they're behind the guy on the bike as he coasts by. I have no problem masking the text, but the shadow still seems to come through (you can see the shadow on the guy's tan jacket). How do I also mask the shadow so it appears behind the guy?
As always: Pre-compose, then mask the result.
You need to duplicate your bottom footage layer, move it to the top, then put your track matte (white solid layer 2) above the copy of the footage and change the track matte to Alpha.
You only need to do the roto where the guy on the bike is in front of the shadow. It does not look like you need to roto the wheels of the bike or his legs.
You also need to cut out all of the holes. Rotobrush is your friend here. I'd just apply Rotobrush to a copy of the footage above all the rest. I think that would be easier than trying to mask all of those shapes by hand.
The blue mask lines are how I would do this.... and I'd only do the frames necessary to cover the shadow.
This is great, thank you!