What do Seventh Day Adventists believe about baptism? What are the Adventist's beliefs about the role of the Holy Spirit in baptism?
The fundamental belief of the Seventh-Day Adventist church on baptism states.


  Baptism is a symbol of our union with Christ, the forgiveness of our
  sins, and our reception of the Holy Spirit


https://www.adventist.org/en/beliefs/church/baptism/

Practically the baptism of the Holy Spirit and baptism for repentance can be separated. In regards to the baptism of the Holy Spirit Adventists do not expect a physical manifestation or 'charisma' experience to happen in the person and it is a much more personal experience in experiencing the presence of God in their life.  This experience often proceeds and is a catalyst for the water baptism.