Landlords dog (3M) getting increasingly agreessive with my roomate (30M)

Hi everyone,

I’m looking for advice on a situation that’s starting to worry me and is getting harder to manage.

I live in South Africa on a shared property where my landlord keeps a ~3-year-old, large boerboel/ bull mastiff type dog (intact/unneutered), and a very big/ strong dog.

When we first moved in, there weren’t any major issues, but over time, the dog has become increasingly aggressive toward my roommate specifically. I haven't noticed too many warning signs, he does initially growl when we open the gate to the parking area, but he is usually asleep or lying down, and stops when he realises who it is. But no real specific stares or stiff posture, just running around and jumping up on myself or roommate/ nipping and biting my roommate.

For some context;

1. R (the pups name for post) lives outside in a small front area with very limited grass/ in the car park of the property. In South Africa, most if not all properties are gated and have high walls for safety. He often gets out as the main gate hasn't been working well. He's also a "security" type dog, aka there to protect the property, as he's an intimidating-looking breed it keeps any potential robbers away.

2. Another dog (a beagle) who lives in the same section as R but in an enclosed caged area with the chickens the landlord keeps on the property.

3. R hasn't had any other aggressive behaviors with other tenants and is fine with another tenants small terrier type dogs.

4. R jumps up often and will try to get in your face (dunno if this is just excitement/ attention seeking), and he's often very excitable when we get home. He's often alone all day/ outside all day.

5. He has a strong prey drive and has tried to get my cat when she followed me out one morning ( I didn't know R was out when she followed me to a separate gated pool area)

My Roomate, call him T, works in security, and is a large, intimidating-looking guy, and does carry himself quite assertively. He also Conceal carries (for work).

He's more a cat guy and is rather neutral/ apathetic to the dog. When he comes off 12+ hour shift, he pretty much gets out his car and heads straight to bed (minimal interaction with R).

The issue is R has moved from guarding/ jumping up to nipping and biting him. Once tearing a shirt and once biting him (thankfully not breaking skin). This is obviously frustrating for T.

As of late, T has had me wake up with him to distract and / or contain R so T can get to his car and leave for work. This isn't a long term solution as he leaves at 4am, and this affects my sleep and schedule, I am usually up an hour later and need my sleep (work with kids and need every hour of rest I can get tbh).

Is there any advice on how to proceed? Moving out isn't an option currently.

Can this be improved with training or positive exposure, treats, or similar, given that the dog has already bitten?

What are safe ways T can build a relationship with the dog, or is separation the best option going forward?

We’d really like to de-escalate this before it becomes more serious.

Any advice would be appreciated.