Combine the mushrooms and onion in a food processor and pulse until they are finely chopped and resemble the texture of ground beef.
Heat the olive oil in the largest saute pan you have over high heat. Once the oil is hot, add the mushroom and onion mixture and allow to cook, stirring occasionally for 10-15 minutes. During the last minute of cooking, add garlic and red pepper, stir to combine, and allow to start turning golden brown and fragrant. Remove mixture from heat and allow to fully cool before combining with other ingredients.
Preheat oven to 400 degrees F. In large bowl, combine ground beef, bread crumbs, grated parmesan, egg, fresh basil, and cooled mushroom mixture. Use hands to thoroughly mix but try not to over work the meat. Shape into 12 evenly sized slider patties.
Bake in preheated oven for 20-25 minutes.
Add marinara sauce to small pan and heat over low heat until heated through.
Split Martin's Potato Rolls and toast in hot oven, open side up, for five minutes.
To assemble sliders, dip each slider patty in the hot marinara sauce and place on top of toasted Martin's Potato Roll bottom. Cover with Italian cheese blend. Add roasted peppers, if desired. Return to oven for another 5-10 minutes to allow the cheese to fully melt.
Serve with remaining warm marinara sauce. Enjoy!
Makes a dozen sliders. Nutritional info based on a single slider as a serving.