You should also know that you already use the “rolled-r” sound to speak in English. No, you do not have to be Scottish to roll your “r” when you speak. It is a very common sound, and is used all the time. However, unlike in Spanish, it is the sound English speakers make when pronouncing a “t” or a “d” between two vowels. Let me give you an example.
Try pronouncing the word “butter.” Did you notice how quickly you flicked your tongue off the roof of your mouth to pronounce that “t” sound between the “uh” and the “er?” That is actually the same sound as the single “r” in Spanish. You can practice flicking the tongue with other familiar English words like batter, letter, better, water, Peter, liter, and so on. But if you still have not got the hand of flicking the tongue you can practice with “d” words, say, “ladder” and see if you make the same quick flick of the tongue between the “a” and the “er.” Do not try to pronounce it the way the English do. What you want is a normal, average American accent, where you soften the sound of the “t” and the “d” so that it just rolls off the tongue.