It is highly speculative whether this has any relationship to the word rasp 'to scrape'. Almost all the Latin and Greek roots we are studying are bound roots. They may or may not have affixes. They are divided into two different types depending on where they attach to the root. The two types of affixes also differ in how they affect the meaning of the word.
Prefixes modify the meaning of the root in some way.
Often, they provide spatial information about an action named by the root. This is necessary to make a sensible English phrase. English grammar requires that the verb is followed by a spatial preposition. Suffixes have two functions, which we'll discuss in WebLecture 1.4. Their most important function is to indicate the part of speech of the word.