user: Question: How many people were first elected when John Roane was the incumbent?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Virginia 2', 'James Trezvant', 'Jacksonian', '1825', 'Re-elected', 'James Trezvant (J) 100%']
SQL:

assistant: SELECT COUNT("First elected") FROM "Table" WHERE "Incumbent" = 'John Roane';