Looks like this positive displacement compressor would be the right choice. A roots-type blower indeed works by trapping a fixed amount of fluid and forcing it towards the discharge. The key parameter is the displacement volume, i.e. how much volume of fluid is trapped and moved per revolution. If you have the spec sheet of the blower, it likely contains such information.
Then you may want to model the volumetric efficiency, i.e. whether you really get that much of volume moved per revolution. This block has an analytical equation for extrapolating from a given nominal condition, or the percentage may change as a function of pressure difference and rpm, which you can use a 2D lookup table to specify the volumetric efficiency. You'll need more information from either reference data from the vendor or your own test data to parametrize this.
Limitation: you can only specify a fixed value for the Polytropic exponent and the Mechanical Efficiency.
