Absolutely.
I've done countless hours on Trainer Road.
I can set a power level in erg mode, lets say 200W.
I will then vary my cadence, anywhere from 50 rpm to 110 rpm. At the lower cadences, my HR is lower by up to 10 bpm, than higher cadences. So my muscular effort is taking the burden. Its around 85 rpm my HR begins to rise with increased cadence.
By cycling at higher cadences 90+ rpm, you can train your body to become accustomed to long periods of non stop pedalling without burning out your legs. Cardiovascular system recovers very quickly compared to glycogen depleted muscles
My max duration for non stop pedalling is 3 hr 15 mins, some do a lot more, but I'm 55 now. It usually takes me 1-2 months of Trainer Road sessions to get my heart rate to track power level without too much drift over 3 hr sessions.
That's when I know I'm cardio fit.