catesetinae try your patience. Sometimes you can't even see the roots to tell how long they are. I also go by a couple of other signs to determine when to start watering.:
Leaves - when they start to spread out (from the tight little bundles they start with ).
Roots - after the first group of roots has started to elongate, you'll see a second flush of roots at the base of the pseudobulbs. Let those get going well, and then you can start watering.
Before that, put the watering can where you can't reach it, and keep your hands in your pockets
so you aren't tempted to grab it. It is better to wait 2 or 3 weeks after you could have started to water than to do it 2 or 3 weeks too soon. You are probably about 2 months away from watering, at least for the plants in your photos.