Step 1Heat the oven to 200 degrees.
Step 2In a small saute pan heated over medium heat, toast the fennel seeds until they are lightly colored and fragrant, 2 to 3 minutes, stirring or shaking the pan frequently. Grind the fennel seeds to a fine powder using a mortar and pestle or coffee grinder.
Step 3Wash the grapes, and clip them into small clusters. Place the clusters in a large bowl and drizzle over the grapeseed oil. Toss the clusters so all the grapes are coated. Sprinkle over the fennel powder and sea salt, then toss again to make sure the spice and seasoning is evenly distributed over the grapes. Place the prepared clusters on a baking sheet.
Step 4Roast the grapes until they are well-shriveled but not burnt, 2 to 3 hours.
Step 5Eat the grapes hot or at room temperature. Roasted grapes will keep for 2 days, unrefrigerated.