SurreyAlan I have a slightly different situation, as I don’t have a dedicated air fryer. I have a countertop convection oven that has an air fryer function. For typical things that you would use an air fryer for, it does quite well.
I agree that it seems a little hard to believe that meat that you would normally roast would benefit from an air fryer. IN general, the reason for slowly roasting a piece of meat is to give it an environment where the collagen in the piece of meat can break down. Collagen in its native form is not a lot of fun to eat. But given (lowish) heat and time, collagen breaks down into gelatin. Gelatin adds the sensation of moisture to the meat, and makes it super yummy.
When roasting a piece of meat, there are several things you’re trying to accomplish at once. The combination of heat and time causes fat to render, collagen to convert to gelatin, and the proteins in the meat to transform from their raw state to a cooked state if they are on the inside, and the proteins on the surface to undergo the Maillard reaction that causes browning. Low and slow BBQ smoking sets up the same sort of environment.
Most conventional roast beef recipes call for an initial roast at a relatively high temperature, followed by a longer roasting time at a lower temperature. The initial blast of heat gets the browning going, and the second part accomplishes the cooking of the fat, protein, and collagen.
An air fryer would help with the browning, but is probably not ideal for inducing collagen breakdown. I suppose you could make the argument that part of air fryer is the fan that moves air around, and that air movement leads to faster cooking between getting rid of hot and cold spots and increased convection. But that’s also what a convection oven does. I would say that’s really the difference between roasting in a convection oven vs. a non-convection oven, and not a factor for the air fryer specifically.