Don't worry about damaging roots... but get some good premixed soil like Fox Farm-Ocean Forest, or Fox Farm-Happy Frog. If you can't find any FF line of soil at your local nurseries... I'd say order it online. it's worth the weight in bud... not literally, but backyard soil man? haha thats funny. FF soil cannot be found at wal mart, home depot. But go to your local nursery and if they don't, ask what they advise is similar. When you do transplant, water it/them, put the stem in between your index & middle finger, cup your hand over the soil, turn upside down, and place the plant in your bigger potted soil mix. Try to keep the backyard soil moving around in your hand to a minimum. Damaging the roots could stress them out or even kill them.
Btw.. FF soil will feed your plants for about a month. By then you should be flowering. Get yourself some bloom nutrients, and away you go