You could use either parentheses, dashes, or commas, to clarify the grammar of the sentence. The information in question is extra information about the subject of the sentence, Albert Einstein. This kind of information is called an appositive.
When you use parentheses you are indicating that the information in them is a kind of aside, and not essential to the sentence.
Albert Einstein (a Nobel Prize winner) is one of the most important scientists of this century.
When you use dashes--which are em dashes--they are used for emphasis and explanatory information that is closely related--it is separated from the rest of the sentence.
Albert Einstein--a Nobel Prize winner--is one of the most important scientists of this century.
You could also use a comma before and after the words in question. This makes it a more seamless phrase within the sentence.
Albert Einstein, a Nobel Prize winner, is one of the most important scientists of this century.