Roasting time for beets depends on their size. Small or medium beets (2 to 2.25 inches across) take about 40 to 45 minutes to roast, depending on the strength of your oven. Medium-large and large beets (2.5 to 3 inches across) take about 60 minutes to roast. If you have very small ("baby") beets, check them at 30 minutes since they may not need that long to roast.