Luke, I have experienced your dilemma. I use those same bags and 1 gallon pots. Going forward, depending on the length of the cutting, I put about an inch of mix at the bottom of the bag below the cutting. This means that there is really only 5 or 6 inches of the cutting actually in the mix. That way even if roots develop near the top of the soil in the bag, I'm still able to cover those roots in a gallon pot.
However, if you have cuttings that you already put all the way to the bottom of the uline bag, there are two possibilities:
1. If the cutting put out roots at the bottom and not originating near the top, near the soil line, then you are OK. In this case then you can just plant in the pot, and an inch or two of the cutting that was formerly covered in dirt will now be exposed. This is OK because the root system is still intact.
2. If the cutting sprouted roots near the top around the soil line, you are in a bit of a pickle. I had one cutting that did this. When I put it in the pot I just barely covered the roots that had formed near the top of the cutting. So when I took it out of the humidity bin, it was very difficult to keep the top of the soil moist. These top roots ended up shriveling up, and the cutting died. I would not advise putting into a gallon pot. You will need to find a taller container. A two gallon pot would be tall enough, so that is an option. If you don't have those (or don't have the space for that yet), you could try things like 1 or 2 liter soda or juice bottles. Those should be tall enough. If you must use the one gallon pot, you'd need to mound up the soil a bit to cover all the roots on the cutting, and then maybe use plastic wrap over top to keep the moisture in. If you mound it up but don't cover the soil it will be difficult to keep it moist unless you water frequently.
Good luck
Rob