Start with roasting the mushrooms. Be sure the gills are scooped out before slicing.
Preheat oven to 450. Use parchment paper on a large baking sheet for mushrooms.
In a bowl, toss the mushrooms, oil, garlic, spices and salt & pepper. Arrange on baking sheet without overlapping. Roast for 10 minutes, turn mushrooms over and roast another 10 minutes, until nicely browned.
When done, remove from oven and return to bowl.