I'm so sorry for your loss

it is so hard to lose our fur members.
Such a fun but tough decision. So many ways to look for your next fur member addition. Puppies are fun, but man they are work. But like Paula said you get a clean slate to work with.
I fostered dogs and cats for a long time. Their true colours will alway show after a period of time when they are more settled. A good responsible rescue will allow a trial period, and that period should be 3-5 weeks although some only like the 2 week period.
Reputable breeders sometimes have their retired dogs looking for new homes. This will give you a dog that had the balanced temperament and characters that are most sought after in that breed and an adult dog. (Notice I said reputable breeder, not a backyard cash grab breeder. )
Shelters have dogs of varying ages and breeds and some shelters allow you to put your name on the list for a specific breed and / or age.
Then there are breed specific rescues, like the greyhound rescue, golden retriever rescue etc. But for some rescues you'd need a lawyer to navigate their policies for what you can and can't do and if you have kids under 14 most rescues won't let you adopt. STUPID. Because I fostered (their) dogs with kids. Also, most rescues want a fenced yard and aren't willing to negotiate that despite atthe quality of life a dog can have on a farm. Anyways, pros and cons on both sides of that fenced yard.
I would like to mention it is important to remember ALL dogs have the capability to attack. Always. It is in their DNA for thousands of years. Despite domestication and doing everything right these things still happen and the family pet will always have the potential. I don't care how loving and sweet you think your dog is, the potential is always there.
I have my left thumb with scars and loss of feeling at the end of my thumb because a little

su at the local park latched onto my hand and ripped it to shreds almost tearing my thumb off. Attacks aren't always from the large breeds or a specific breed.
My friend had a golden retriever and she was a nasty, nasty girl. She bit kids, family, UPS guy and my friend who is a groomer when I took her there (no one could brush or bath her) but I will be honest, this dog needed an alpha, Exercise and discipline.
I fostered a little chihuahua. What an

! He bit everyone within 5 mins of being here. Once. But that dog is never to be trusted. Ever. Trigger happy.
So here's the thing. Finding a rescue that will tell the truth and having experienced what the 'truth' is, will be the challenge. Any dog we take in from rescues or shelters we must take assuming they are a kid from the block and assume worst case, but the chances are you'll end up with a fantastic dog. But there is also a chance you won't. The SPCA can't tell you what the dog is like in a family or home environment because they don't provide one. They go on what they are told if the dog is surrendered, if they are told anything. They can not adequately assess a dog in the SPCA institutional environment. I did dog assessment for the SPCA for many years and have always expressed concerns about institutional results of a potential adoptable dog.
With that said there are certain breeds I would not consider from a shelter or a general rescue group. But those breeds I would definitely consider from breed specific rescues.
And puppies ... Clean slate for sure, but DNA that is thousands of years old is always there. And as you know from your Rotti, even having them from puppyhood does not exempt them from what we consider uncharacteristic behaviour.
I have a German shepherd and a golden retriever. Complete opposites but they compliment each other and for my home it's the perfect combination. Both pure breeds and from puppies. I am also very aware that despite having from puppies that they are disendents from wolves and will always have the capabilities that we try to domesticate out of them.
It's an exciting journey with so many possibilities to choose from. Is there a breed you have always loved and wanted?