when to move seedlings into veg

hey ive got 9 seedlings they have all been put into the 3in cubes and some of them are starting to show roots on the bottom. ive got 7 of them with a couple small roots and two that are a little slow. my question is i want to put all of them in veg at the same time how long can i have the roots out before i have to put them into veg. there under 2 t5s and are in a try on a heat mat. also will the heat mat hurt the roots thanks

They wont go into veg until after 4 weeks(the seedling stage)

They will start to show vegetative growth after the roots are established. I'm not sure I understand your question. Aside from taking care of them in a proper standard way there is nothing you can do to speed up the process of going from seedling to vegetation to my knowledge. The heat pad is great for roots, seedlings, and clones. Just as long as it's just warm and not hot.

Are you trying to say you wish to put them into FLOWER at the same time?

ok well the thing im was worried about is that the roots coming out the bottom touching the tray wont burn or get messed up cause of the heat pad. and i was trying to say is i just was hoping to have all 9 go into veg stage at the same time cause im doing a scrog. thanks for the info

the way i do it. seedlings go in coco plugs on a tray, under a dome for a week. this is usually enough time for the roots to start shooting out of the plugs. then they go into soil and given another week for root development. they are then placed under a metal halide to complete the vegetation stage for three weeks.

technically they are vegetative after sprouting and showing signs of growth.