The rolling r (and rr)

[Rusty]

Originally Posted by ElDanés

I knew you were, so I edited it the fastest I could.

Yep, but in this case I thought it would be hard to hear if a speaker use a dental- or alveolar sound.

Yeah, you've got to be quick!

Quite right. Hearing how something is pronounced doesn't necessarily teach you how it is pronounced. I'm only suggesting that you mimic, as best you can, what you're hearing from a native speaker. The very best way to learn how something is pronounced is to ask for help, as you have done.

You figured out on your own that the book wasn't teaching you the correct method. That's because you're listening to the result.