user: Question: What district has a Democratic leader from Roby?
Columns: ['Senator', 'Party', 'District', 'Home Town', 'Took Office']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Bill Ratliff', 'Republican', 1.0, 'Mount Pleasant', 1989.0]
SQL:

assistant: SELECT "District" FROM "Table" WHERE "Party" = 'Democratic' AND "Home Town" = 'Roby';