Can Drainage Areas be imported from graphics?

Not directly.  InRoads can import from a text file.  Try exporting the vertices of the graphic shapes from MicroStation’s Tools > Dimensions > XYZ Text > Export Coordinates.  This command will export the XYZ data for graphic elements selected.  Then this file can be edited to add the area ids for the point data and then it can be imported into InRoads *.SDB file with File > Import > Drainage.  Search Help for “File Characteristics” for drainage formats.