Hi there Megz.
I also have just the one BP, and I wanted to chime in here because mine does
exactly the same thing as yours! He used to be a great eater when he was young. He'd immediately strike at his f/t rats and eat them right away. But then, when I'd had him for about 7 or 8 months, he became finicky.
He stopped accepting the rats, and just wouldn't take them no matter what I tried. In the end, he went for two months without food! During spring, no less. And in the last month of it, I was away for a school course. So I wasn't there to offer food to him... when I got back, you better believe he ate that rat!
He still does exactly what you describe (going up to the rat, sniffing it, turning away) and tends to roam around his tub like he's hungry. I'm not worried though, because I figured out exactly what to do for him.
1. I have to give him a little extra heat for the day of feeding. He seems to like it hot! (I do this by putting a hot water bottle on top of his tub for that day. Wrapped in a towel, and covering the whole tub with a towel as well.)
2. I have to
really warm up the rat! I'll thaw it in warm water, then at the end when it's definitely thawed, I'll give it another go in extra-warm water. And then, I take the hair dryer and blast it at the rat's head to really toast it!
3. And finally, I have to place the rat in the tub,
inside his warm hide. He won't touch it if it's outside the hide

And then I put the towel over the tub and walk away for 3 hours. Nowadays, almost every time the rat is gone!
Hopefully this eases your mind a little bit when it comes to Roxy's behaviour. I promise, she's not traumatized!! She's just... being a ball python

The things we do for them!!