Worksheet
The reference sheet works this out in the key of A. It's the same form everywhere — only the letter names change. Fill in the chord for each Roman numeral below. The quick change (bar 2) and the turnaround (bar 12) are marked the same way as on the reference sheet.
Check yourself: IV sits a perfect fourth above the key, V a perfect fifth — and every chord you write should be a dominant 7th.