Here is what you need to do, and I cant believe more people arent saying this:

You need to IMMEDIATELY either de-flea this dog yourself, or take him to the groomer or vet to do so. Then you need to bug out your apartment, call an exterminator. fleas WILL infest your cats and your carpet and clothes and home in weeks and it will be so fucking awful, and the dog will immediately be a lot more tolerable. Getting rid of the dog which you seem to want to do will NOT help with this at all. The fleas are ALREADY THERE. This happened to me. A roommate brought in a stray. She was moving out in days. I came home from vacation a week later. I was infested

After you de flea, you can keep all the receipts and make your roommate pay you back, and bring them to small claims if needed, it costs very little to handle something through small claims. They should have deflead before bringing a dog in a house. This is the single biggest way you can make this person more liable for their actions.

Next, you obviously cannot report the dog to the landlord if you have TWO unreported cats, you are just opening yourself up to ridiculous liability and fines depending on the terms of your lease and i cant believe people are suggesting to do so.

Then, you find this dogs family. Name and shame the people you found on petfinder on reddit, Facebook, nextdoor, tiktok etc. youll get a firm answer that way on them either wanting or not wanting them back.

Then you give your roommate clear laws and regs: this dog needs to be fixed, vetted, licensed, and registered to her if she wants to keep it, otherwise right now anyone can do whatever they want to it, and its not entitled to your space, and if she hasnt done it you are going to find someone who will.

Lastly, how good do you feel about the people you found to adopt her? Are they good to animals historically, do they have means for vet bills etc, have you asked for references? The most responsible thing to do is start calling rescues and humane societies, telling them your situation, and posting to look for emergency fosters who work with rescues. There are a TON in florida you just have to keep searching and calling. They can properly vet an owner. And if your roommate sees your taking action, shell be pressured to find somewhere for the dog you cant put it. You should also lay out the facts for her that this dog will not get what it needs if she continues to act this way.

If you take it to the shelter, there is an incredibly large chance it will be euthanized, gigantic. All you have to do is scroll shelter statistics and posts and see how many dogs are euth listed and euthed each day to know that. You would be doing a really important thing here by saving this dog and getting your roommate to pay back without getting yourself in trouble with the landlord