Roots and when to transplant

In past years I have waited until the baby plants are overgrown to transplant and their root system is well developed and it makes it very easy to move.  This year I was attempting to transplant them before they got overgrown, but I'm running into the issue of there not being a root ball.  The dirt falls apart and I end up moving a scrawny little plant with bare roots.  I'm no expert, but I can't imagine that's too good for the plant.  Most of them seem to be alright and I think only time will tell if the plants are going to make it or not.

When I moved the lettuce for example, they had a tiny little root system.  I googled "root ball for lettuce" and it led me to this informative site. According to its diagrams, there isn't really a "root ball" for lettuce.  So that leads me to believe that it's just about being very careful when handling delicate plants.  The lettuce is particularly scrawny and again I'll just have to be careful.  I don't think there's much chance of me splitting the multiple plants into individual ones at this point, so we'll see how they grow