I am a subdeacon and have served in both ROCOR and Antiochian parishes as I moved around the country.
A Subdeacon's primary role is to serve as an assistant to the Bishop when he visits a parish, to assist him in robing and disrobing, provide him the symbols of his office and assist him by holding the Dikirion (Greek: δικήριον or δίκηρον) and trikirion (τρικήριον or τρίκηρον) or liturgical candlesticks, used by a bishop of the Eastern Orthodox Churches to bless the clergy and faithful. Our placement is so the bishop need only hold out his hands and the candles are there for his use and our hands are there to received them and return them to the altar. We also position and remove the orlet or eagle carpet that the bishop stands on when he blesses the people or gives his sermon. Inside the altar the subdeacon is basically at the bishops beckon and call for what ever the bishop wishes to be done. After the service I usually follow the bishop and assist him during the visit by getting his food, holding down the flood of those seeking to crush him as they seek his blessing etc. In ROCOR , I was assigned a retired bishop to assist at Liturgies that he was present in but not serving. As many Bishops are elderly, often the subdeacon assists them up and down stairs by offering them a steady arm or a hand and assures that they do not trip or fall injuring themselves.
When the bishop is not present I serve as a senior altar service, train new altar boys, monitor the behavior of the boys behind the altar to assure respect and humble behavior is exhibited during the liturgical services. After wards I assist in the clean up of the Holy place assuring dust and candle spills are taken care of properly. At the end of the service I lead the prayers after communion for the congregation (a pious practice peculiar to my current parish). I also am the Catechumen Director in my parish and assist the inquirers and catechumen in meeting requirements that will lead to their baptism/chrismation.
