Devotions to the Saints play a role in Christianity practically since its inception. Saints may be reverenced; they may never be worshiped. Devotional practices should be to further our love and commitment to our God who alone is to be worshiped.
The Church has a calendar of Saints to whom we pray, asking that they help us in our petitions to the Lord. There is human comfort in asking the Saints, our friends and advocates to join us in prayer for all our needs.
Jesus asked us to "knock and the door will be opened," He is saying that if we are persistent we will have our need met because of our faith and trust. We ask the Saints to join us in this persistent prayer because they are our friends, just as you would ask a personal friend to pray for you and with you. Is this not intercession? Of course it is, we need one another!