As a default in Revit, when you attach a column to a roof (or another sloped element), the top of the column remains flat. If you would like the column top to be profiled to match the surface above you will need to adjust one of the instance parameters.
Firstly you will need to attach the column to the sloped surface, and then if you select the column, in the properties, go to the ‘Attachment Justification At Top’ and set it to ‘Maximum intersection’. The column will now have the top profiled to the sloped surface.
You can also set this parameter to ‘Intersect Column Midline’ for the connection to be on the middle of the column.
This works for the base connection as well. Once the column is attached you will be able to change the ‘Attachment Justification At Base’ parameter in a similar fashion.