Agreed with the above- biting is always for a reason (it just happens more when you haven't figured out that reason lol)
The main reasons for any behavior= attention (eye contact, a vocal response, proximity, physical etc), escape (to get out of a situation, avoid a task or person or environment), tangibles (to get a preferred food or object) and sensory/automatic (e.g., crying when injured, itching a bug bite etc).
When your bird bites, it is probably doing it for one of these 4 reasons.
If your bird is screaming, do not come back into the room until it stops for a set period of time. You will need to start this time period off very short if you have made the mistake of entering the room during scream-fests previously. Now, there are different types of screams, but your sounds like it is screaming to get out/attention and in that case, it is unlikely a fear scream (which should not be ignored). Fear screaming sounds different and usually is pretty obvious-- you don't want to ignore a frightened bird, but it doesn't sound like that is the issue here.
You should also use key words and terms to help your bird judge how long you will be gone and what you are doing. E.G., "Going to work" or "going to the store" --I use work if I will be gone more than 4 hours, and "store" for anything under 3. I say be right back if I am just stepping away for a few, and I even say stuff like "wait, washing my hands" or "going to the bathroom". My bird knows these phrases now and is okay with be doing a lot more because she can anticipate and knows the routines associated with each. It also helps to talk from room-to-room to your bird BEFORE the screaming starts.
Also sounds like your bird is entering puberty..2.3- 3.5 years is typically the norm.. They do change behavior as adults and the rules about touching them etc also change. Head and neck only (if you have a bird that lets you pet it) and no shadowy spaces like huts, boxes, tents, nooks etc....no under furniture...
10 hours of sleep nightly = very important as well.
Your roommate may be the preferred person (which is always the risk with birds) but DO make sure he isn't touching your parrot places other than the head and neck. Also, if anything bad or stressful has to happen, the more preferred person should be the one associated with that trauma lol.
Also- what is the longest you have let her scream before coming to get her in order to stop the noise? Waiting them out effectively can take many hours...I'd buy some Macke's earplugs (the putty/silicone type) and stand your ground. You might start the window of silence at 10 s---you should always try to prevent it by saying what you are doing and talking room to room, but IF you are leaving, plan accordingly so that you do not return to that room until screaming stops for a set period of time (even entering to get a phone or keys= attention).
So, lets so you start at 10 seconds, that means that you give your parrot 0 attention until the screaming stops for at least 10 s (1 Mississippi, 2 Mississippi,, 3 Mississippi,etc ) If the screaming starts before the 10 s is up, you have to start back at 1--- you need a solid 10 before coming back. The count should happen in your head (not where your bird can see you). Remember, it is super important to prevent this by making sure they get enough sleep, have a large enough cage, spend plenty of time out of it, proper diet etc--- BUT what I am describing works for a bird who screams for attention. If you know the screaming is to get you or to get out of the cage, try the counting thing. WHEN the screaming stops for 10, immediately go in and in a quiet voice, say thanks for being quiet and open the cage or do whatever you think it was that the bird wanted to begin with. REMEMBER- talking about the bird, looking at the bird, getting closer to the bird, entering the room etc are all forms of attention...You can give any attention you want but if you are sure it's attention screaming, the second it starts you need to act according, and everyone needs to be on the same page about the rules...especially your mate. Once 10 seconds silence is easier, move the threshold to 15 until that is mastered, then 20 etc. If you think your bird is about to scream but hasn't yet, you can always pop back in (there is nothing wrong with doing that, as long as the screaming hasn't started).
Screaming is natural for them-- it's how they communicate with their flocks in the wild... BUT, what you don't want to do is accidentally encourage the behavior by proving that it works.
That is why you want to do all that you can to PREVENT it (by talking about what you are doing, using routines, speaking room-to-room etc). Note: WHENEVER you start ignoring a behavior that previously worked, the behavior WILL get worse before it gets better. The worst thing you could possibly do is break and enter the room after putting a behavior on extinction/ignoring it because then you just proved that the bird can get your attention if it just screams louder and longer--- slot machines work on intermittent reinforcement that is the quickest way to get a human or bird to repeat a behavior (fail to reward and then suddenly reward---which is why it is essential that you commit to this once you start ignoring).
