In a seperate bowl, coat the halved grape tomatoes with the olive oil, season with salt and pepper. Place the tomatoes in a single layer on a cookie sheet, and roast for 20 minutes in a 350 degree oven.
On a mandoline shave the brussel sprouts thin into a bowl.
In another bowl, combine the mayonaise, rice wine vinegar, the juice of half of the lemon and the brown sugar, and mix to incorporate. Salt and pepper to taste.
Pour the dressing over the shaved brussel sprouts, and stir. When the tomatoes are complete remove from pan and stir into the slaw.
Allow to sit for a short period and serve on a sandwich or as a side dish to lamb, or chicken.