Meatloaf: combine all meatloaf (not glaze) ingredients in a large bowl.
With your hands, mix the meatloaf until everything is well-defined.
Place all mixed meatloaf ingredients on a parchment-lined sheet pan and, using your hands, shape into a bread loaf-shaped rectangle (around 9 x 5 inches) Pack it fairly tight so that everything stays together.
Preheat oven to 425 F (220 C) and then add your meatloaf to the oven and reduce heat in the oven to 350 F (177 C).
Set a timer for 15 minutes and start to make your glaze.
Sriracha glaze: add all glaze ingredients into a small saucepan over medium heat. When brown sugar has melted and all ingredients are combined, take your glaze off the heat.
Pull the meatloaf out of the oven after 15 minutes and with a brush or spoon, paint the glaze on top every 15 minutes or until an hour has elapsed. After an hour the meatloaf should be done, but you can check with a thermometer if you have one. The interior of the meatloaf should be at 155 F (68 C) when you pull it out. Carry-over heat will bring the meatloaf to 160 degrees F.
Sandwich assembly: if the meatloaf is in the refrigerator you will need to warm it. You can do this on a plate in the microwave for around 60 seconds or in a skillet over medium heat for about 3 or 4 minutes per side. If you choose the skillet, add your slices of cheese when you flip the meatloaf to cook the second side. This will allow the cheese some time to melt.
Once the meatloaf has been warmed fully, open your bread roll and add any condiments like mayonnaise to the bottom and/or top of the roll. Place the cheese-topped meatloaf slice in the sandwich and top it with pickles. If you have store-bought crispy onions, add those on top of the pickles and close the sandwich.