Preheat oven to 400 °F and line a baking sheet with ℉. parchment paper.
Scatter tomatoes over pan. Drizzle with olive oil; sprinkle salt, red pepper flakes, and black pepper. Toss to combine. Roast until tomatoes are slightly charred, 25-30 minutes.
In a large bowl, using a fork, smash the avocados. Add lime juice and garlic. Mix to combine.
Top the toast with mashed avocado, roasted tomatoes, feta, and arugula. Garnish with black pepper. Serve immediately.