I can only give an answer here about my experiences with the J7+/J9+.

I installed a J7+ in my sister's home and she has quite high door thresholds in two rooms. One around 1.5cm and one around 2cm (unfortunately I can't say exactly). The vacuum cleaner has always been able to get in and out of the rooms. However, it has often had to get a good run-up and the underside of the vacuum cleaner is affected accordingly, but this only has a visual impact.

But to be honest, I would also buy additional ramps or at least test the device beforehand, as every doorstep is built differently (sharp edge, rounded etc.) and therefore it cannot be said uniformly whether the Roomba generally makes it over them. In general, 2cm is normally the absolute upper limit for robot hoovers.

Just my opinion.

Hello everyone
We can only agree with the opinion of hafi92.
We generally recommend a maximum threshold height of 1.6 cm. In certain cases, more is possible, but we cannot guarantee this.
The safest option in your case would be to work with ramps.

Best regards
Your iRobot Team