what are four roles of proteins?

Since this is not my area of expertise, I searched Google under the key words "protein functions" to get these possible sources:

http://en.wikipedia.org/wiki/Protein
http://www.faqs.org/nutrition/Pre-Sma/Protein.html
http://www.calstatela.edu/faculty/lcalder/ucsb/sld016.htm

In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search.

I hope this helps a little more. Thanks for asking.