Question: What size generator should I have to power my roof air conditioner on a Flagstaff 620 st popup trailer?
Answer: Since you did not mention the power requirements of the air conditioner, we recommend you research this by looking at the products available through Camping World.
They sell a variety of small portable generators. Honda makes an extensive line of small portable generators. The smallest will provide 2000 Watts of power enough to power a small residential style air conditioner. You may also want to search our site for terms like “electricity’, “power” and so forth to determine your needs for power while RVing.