Just keep in mind, if you treat a small room such as a closet, or anything less than 10ft by 10ft your going to have some serious issues with the low frequencies. Treat the highs all you like, but those low frequencies can be a killer - as I have learned the hard way. The only way, ONLY way is to tame them with bass traps and there are various DIY ones made or ones you can purchase. for DIY the best way to go is with 4 inch thick rockwool but 2 inch and 3 inch is good as well. I used immatation (bought off Ebay) Lenrd bass traps on the top corners and DIY Tube bass traps. If you don't then you'll get the boxy sounding room, with comb filtering, and all kinds of funky crap that you simply CANNOT EQ out.
As far as the RodeNT1A, I've used it for awhile, and I still own it, I think it's a great mic, even for screaming vocals. It's on the bright side, so you'll run into issues with "sssy" sounds, but with a nice De-esser you can work with that, or use the pencil trick. Also, that Rode NT1A is VERY transparent, meaning that what you hear is what you get, very little coloration - except for the brightness of that Mic.