In theory, vacuum robots can go over threshold dividers up to 1 inch (~2.54 cm) high. This is why Roomba and friends have their main wheels mounted on springs.
In practice, vacuum robots can easily go over flooring transitions that are less than 1/2 inch high (~1.3 cm). But, thresholds that are 3/4 inches (~1.9 cm) high or more, need to have rounded edges. Otherwise, the vacuum robot might bounce on them.
The video shows a Roomba going over doorsteps of different thicknesses, but all with sharp edges. The robot get stuck sometimes with dividers that are that is 0.7 inches (~1.8cm) high. Though it always manages to free itself.