Pre-heat oven (or toaster oven) to 375 degrees and line a baking sheet with foil or parchment paper.
Place tomatoes on baking sheet, lightly brush with olive oil, sprinkle with salt and pepper, and roast for about 30-35 minutes, until tomatoes are blistered and starting to burst.
While tomatoes are roasting, place avocado in a small bowl and mash, along with lime juice and salt and pepper.
Bring a large saucepan of water to a boil, along with white vinegar and a pinch of salt. Crack eggs into an individual ramekin one at a time.
Carefully, set egg into boiling water. Repeat with other eggs, working in batches if you don't have enough space for all 4 eggs at once. Remove saucepan from heat and let eggs cook for about 4 minutes until yolks are just set. Remove from water with slotted spoon to a paper towel-covered plate.
Spread a generous layer of mashed avocado onto each slice of toast. Top each slice with roasted tomatoes, a slice of prosciutto, and an egg. Top with salt, pepper, and red pepper flakes, if desired.