We're looking at compact cots so we can keep our baby in our bedroom (space consideration) and its the same width as the bassinet but longer and has two different height settings. It also meets current saftey standards. Is the hight why its considered safer than a bassinet when baby starts rolling? Any other reason?

When baby is rolling, it is important that they have the space to roll well….. this refers to the overall space of the cot, not just length (& height) but width as well.
This is why using a portable cot can be helpful when there is not the space for a regular size cot.
Whatever type of cot you use, it’s important that the mattress is placed at the lower setting, as the upper setting is for the use as a bassinet.