I'm growing a beefsteak in a 3" net cup with a much finer mesh than that and the roots went through just fine.

the small roots will have no problem i don't think..

this is my first year using a net pot for tomatoes and i know that once a tomato plant reaches at least 4ft high some of the roots (center of main vine) are at least 1/4~ inch in diameter. it probably won't kill the plant, but maybe limit it's growth if the larger roots become jammed in a tight hole. i'm probably going to cut a X section from the center bottom of the net pot where the main vine/rockwool will be sitting on, just as a precaution.

You can cut your own hole in the netpot, the only problem you might encounter is the medium going throught it. Maybe keeping an eye on the roots and make the proper cut when it's too fit, but it might become a rigorous and accurate task.