@Bryce told me in another topic (emphasis mine):
As for your question about Ramp Testing, we totally recommend Ramp Testing on both bikes. Your FTP on your road bike is likely significantly higher than your FTP on your Triathlon Bike, and the only way to find out is with a test
The stress of a Ramp Test is fairly low, so just be sure to give yourself a few days in between tests.
From: Group rides are a lot of TSS. Accomodate them or skip them?