Starting indoors then moving outside

I've got this attic that's attached to my room that I was thinking of starting a couple seedlings in. Everyone says you're supposed to let them grow a couple inches before moving outside...

Thing is, it's pretty stuffy up there. Is that a problem? My roommates wouldn't approve so I was thinking I could have them in the attic during the day and then move them to my room during the night (people come in my room occasionally without warning but no one ever goes in the attic), because it gets cold up in there at night.

What kind of light(s) would I need to just get a couple seedlings to the 2-3 inch stage?

And any tips on moving them to my outside area (in a big forest close by) once I do get them to that stage? I was planning on starting them in rockwool trays.

germinate the seeds put them in solo cup 1/2 to 3/4 full of dirt bout half inch deep root down dont touch root. kees soil damp put a small light on it and wait you can use small floros put them almost touching plant

Are there any battery powered lights I could use (and have one charging and the other in use, and alternate)?

So is the rockwool a bad idea? Should I just use normal loam dirt or something?