Timothy's role was important because the believers in Thessolonica were being persecuted and they needed a strong leader to guide them and to help them maintain their faith throughout. In addition to this, as a body of new believers, it was important they they be properly led so that they can develop in their faith. It is certainly easy enough for mature believers to wander off the path, and even doubly so for new believers without the proper guidance from an experienced leader. Since Paul was not able to return to lead them, Timothy was a good choice to go in his stead. This was a sensitive role because it required the right amount of leadership to help the people keep the faith without bringing more trouble on them. Timothy had to find a way to strike a balance that would help the Church develop without causing more persecution. I believe that through this work, Timothy was able to grow in both his own faith, and his ability to lead. In helping the Church to grow, he was also growing himself.
Delegating ministry is important in two ways. First, by delegating responsibility to other members, the leader is freed from many of the day-to-day workings of the ministry, allowing him/her to have more time to grow the ministry. It also allows members of the group to realize and utilize special gifts that will help to make the group more functional, and it will make for a more solid group with help to individual members more accessible at any given time.