I'm not sure how you can check while they're in the soil, but many people root pothos cuttings in water. That way you can see the roots grow to about an inch or 2 before placing them in soil. You could remove them from the soil and place them in water, but I'm unsure if that would add additional stress to the plant.

I didn't root them in water because I knew I would eventually want it in soil, and heard that the root system is very different when propagated in water VS soil and could potentially lead to difficulty down the road if you wanted to put a water-propagated plant into soil ...

What you are saying about "water roots" is true for some plants, but not Pothos. They root in water in usually a week at most. Once you've got nice hairy roots started, you can easily move the plants into loose soil.

try using a plastic bag to make a mini green. open the bag every so often so it doesn't mildew.