You will see that your little rosea will not move around a lot and really wont need all that space. I have my adult female rose hair in a medium critter keeper (I think) and it is perfect for her. I will post a pic of her in it for reference when I get a chance. A 5 gallon tank would be plenty of room. A 10gallon would be over kill and a 20 gallon you could put a big 10" T blondi in. Use something like bed a beast for substrate, they like it dry and add a hide, a water dish (do not put a sponge in it) and decorations if you wanted. Get yourself a pair of 10" tweezers (tongs) from the pet store to remove dead crickets and discarded food boluses. That's about it. Then sit back and enjoyOh and if you got a male that is mature he will sadly only live a few years
If it is a mature male it will have tibial hooks an the first pair of legs and the tips of the pedipalps will look kinda like boxing gloves (club shaped).