I'm learning Spanish at the moment too. I was born and live in Australia, but my nationality is Croatian so I have been around European language since I was a little kid though, so I just naturally know how to do it. You'll probably pick it up eventually though. Don't stress.
I think it may be genetic or maybe you can accustom yourself through practice. My native tongue is spanish and last year I moved to Denmark and it has been impossible for me to physically do the kind of noises that the danish language requires. Furthermore, Ive tried to make danish friends roll r's and they cant. LOL
No it's not genetic. But this is why there are accents. If you're learning a new language it's really difficult to sound exactly like a native speaker, because whatever language you grew up with is ingrained in your brain.
I think it's part of the language learning process and much like your ability to learn a language decreasing after a certain set of years, I think the ability to learn to roll R's may be similar. I do wonder if it's related to genetics in a sense though since being able to curl up your tongue is a genetic trait.
I think with practice (and perhaps tongue exercises, seeing it has many muscles?) you'd be able to conquer rolling R's!
