"For I long to see you, that I may impart to you some spiritual gift to strengthen you..." (Romans 1:8-17).
The church in Rome had a good reputation, and so Paul wanted to go and visit those believers and have fellowship with them. He prayed for them, "without ceasing," that God might let him visit them. It was his desire to impart some spiritual gifts to them.
This is a ministry that many of us have. We pray with people not only for salvation and the baptism of the Holy Spirit, but for the "spiritual gifts" (charismatic gifts) that Paul mentions later in (Romans 12:6-8; and 1st Corinthians 12:8-10).
This "ministry of gifting" equips the saints for ministry with each other and with unbelievers. The gifts of the Holy Spirit strengthen and encourage faith among the believers.
The gifts also have an evangelistic function - to draw people to believe in Jesus Christ as Saviour, Lord, Healer and Deliverer. As Paul told the Corinthians, "My speech and message were not in plausible words of wisdom, but in demonstration of the Spirit and of power" (1 Corinthians 2:4,5).
The Holy Spirit`s gifts are necessary as a sign to believers that the Gospel is true, and that they can "live by faith."