Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and devein the shrimp, then wash and quarter the cremini mushrooms.
Mince the garlic cloves and finely chop the fresh thyme and rosemary leaves.
In a large mixing bowl, toss the mushrooms with half of the melted ghee, the minced garlic, chopped herbs, sea salt, and black pepper.
Spread the mushrooms in a single layer on the prepared baking sheet and roast for 10 minutes.
While mushrooms roast, toss the shrimp in the remaining ghee in the same mixing bowl.
Add the shrimp to the baking sheet with the mushrooms and roast for another 6-8 minutes until the shrimp are pink and opaque.
Remove from the oven and immediately toss the hot mixture with baby spinach and lemon juice until the greens are slightly wilted.