Recumbent bike trainer vs actual bike on roller/trainer?

I have a nice recumbent bike trainer at my home with interactive heart rate monitor, rpm meter, interval programs, etc. I originally purchased it to help recover from serious lower back problems, and it let me get a good endurance-type workout without pressure on lower back, knees from running, etc.

Now years later I'm training for a triathlon, and wondering if time on the recumbent bike machine can substitute for a portion of the bicycle training sessions. I realize it's not the same, but with a busy full-time job, childcare responsibilities that don't always allow me to leave the house and the bad weather coming, I was wondering if I might take advantage of the machine I have.

Or is a bike roller the only way to go?

As a triathlon beginner, I'd be grateful for any insight folks may have.

Thank you!