The time it takes to roast raw corn in the oven depends on several factors, including the size and thickness of the corn, the temperature of the oven, and personal taste preferences. Typically, it takes about 20-30 minutes to roast raw corn.

Raw corn can be roasted according to the following steps:

1. Preheat the oven to 400°F (200°C).

2. Remove the outer leaves and whiskers from the corn.

3. Place the corn on a baking sheet or grill.

4. Place the baking sheet or rack in the preheated oven.

5. Roast for 15-20 minutes, then check the corn for doneness.

6. Insert a knife into the center of the corn, if the knife inserts easily and the kernels are soft, the corn is cooked through.

7. If you need a more cooked texture, continue roasting for 5-10 minutes.

8. Remove the roasted corn, you can add appropriate amount of butter and salt and enjoy.

Please note that this is only a general guide and the actual grilling time will need to be adjusted on a case-by-case basis. If you're unsure about the grilling time, you can check in every few minutes to make sure the corn isn't overcooked.