If I remember correctly, and I think I do, Emerson was starter, wasn't he?
I think Delvecchio and Zanneti were rotating in and out of first team, and it would change the way Roma played.
Emerson was regista, someone who had free role to move, even to come in opponents box and finish moves, but not always. Zanneti (when he played) was BWM positioned on left side when he played, and during attack, he would move centrally and free up space for Candela to move in. When he played, Roma usually fielded in 3-1-4-1-1 formation. Tomassi sometimes acted like siting midfielder, and sometimes he was running from deep to finish off the moves. When Delvecchio played, this would become 4-4-1-1, where Tomassi and Emerson would be much more cautious to move forward comparing to previous version. In both formation, however, they defended in 4-4-1-1 shape. Delveccio was striker, but in this system, he played more like winger then striker.
Also, when they would chase results, they would change formation to 3-4-1-2, buy inserting Montela as second striker, and changing Totti with Nakata, who was more defensively active player then Totti was, and at the same time, he still provided enough creativity in attack.
Also, worth mentioning is that Samuel was not always playing as sweeper, but in some modifications of system, they used him as central back.
I agree that this is impossible to implement all in one tactic, as there is so many variations of system they played in. Even with three tactical slots, it is hard to cover all systems they played in during this period of time...