I read the following in a textbook:
In the German-speaking world of Germany, Austria, and Switzerland, there are two distinct ways of pronouncing r. One way is the rolled r as is heard in Italian or Russian. The other is the so-called guttural r that is a sound made near the back of the tongue. In German the guttural sound is used when the r is located at the beginning of a word. For example, rot means red and is pronounced rote, with a guttural sound distinctly similar to a French r. When this letter is at the end of a syllable or word, particularly in the combination er, it sounds more like uh and does not resemble an r. It is similar to a final r in British English. For example, Zucker means sugar and is pronounced tsoo-kuh.
So when exactly do I use the rolled r sound to pronounce a word?