Slowly roll up and down to stretch and massage your spine.
Also try adding some side-to-side movements to target different areas of your back.
Relax into it and be mindful of how it feels; if you encounter an area that feels restricted or tensed, spend more time on that area.
Risks
Rolling directly on the spine (in the middle of the back) might create too much pressure on your vertebrae; avoid that area and focus on the sides of the spine.