Some quick things off the top of my head.

1. Most importantly, put a fair bit of time in developing all of your security policies and standards. If you think you need one...write one!

2. Duties (a bit hard to be accurate without knowing details about your company..but Ill do my best )
a. Administration..Depending on what your environment is like would depend on your adminstration duties (ie. like firewall admin, router acl's, various password admin/resets,....).
b. The IT Sec team should be across is all new projects or new initiatives your company is undertaking and identify any security risks/exposures. (Tip. Its is easier to mitigate security risks with projects during their development phase rather than trying and secure them once they are in production!)
c. Security investigations in case of an incident or breach of security.

3. Try and educate your employees early regarding the importance of security best practises. ie. disclosing passwords etc...

4. I think that a good security team needs to interact positively with other IT Departments, so physical segregation may actually work against you. Although, I know that some may have a difference of opinion

If I think of anything else...I will be sure to post it.

Good luck!!!