Word...I got you covered. I've used rockwool for starting clones and dwc w/ hydroton together now for over 3 years.
First off...what's your medium in the DWC buckets? As I said, I use hydroton but there's plenty of other options. In the end though, it really doesn't matter what your medium is...and here's why:
Short answer....get your roots to hang down into your dwc res at least a few inches.
Long answer...
DWC, as you know, relies on the roots being down into the water. Theoretically, as long as your roots hang into your res a little then you're good. This is due to the capillary action from the roots...same as using a wick system (Google "hydroponic wick system") Me though? I don't rely on that. It's dwc, so in my opinion you should be pumping air/O2/bubbles into your res like they're going out of style. I've got some ridiculously large O2 pumps..one cost me over 120$ with airstone-mania going on. I mean...it's over kill, but it's cheap and it ensure for me I got the DO levels I need in the water. So, if you do something like that...then you're basically going into a combo of bubbleponics and DWC. Which in that case then you're all good...because the bubbles will splash up onto your mesh cups. If the bubble splash onto the uppermost rootzone isn't happening for me, then my water is too low in the res.
HMU with questions.
Peace