The Presbyterian Church is filled with rules and regulations.
Some of these are under the Office of the General Assembly (OGA)
The Book of Order is Part II of the Constitution of the Presbyterian Church (U.S.A.).
This document contains the Form of Government, Directory for Worship, Rules of Discipline,
and the Formula of Agreement. 

Constitutional Musing - # 20 Unicameral Boards 
oga.pcusa.org/constitutionalservices/musings/note20.pdf says:

General rolls are: 
Session (Elders): internal affairs
Deacons: external, reaching out
Trustees: property issues

Deacons specific duties:
Minister to the needy, sick, friendless & distressed.
Duty of compassion, witness and service.

www.pcusa.org/oga/constitution.htm

last updated 2 Jan 2011