Can a hybrid bike seat be used on a road bike? I'm new to road bike riding. At my local bike shop they fitted me for a Bontrager Nebula Plus to replace the stock seat that came with the bike.



The Bontrager website says this seat is designed for hybrid riders. It's hard to tell at this point if my post ride discomfort is from the seat or if I'm still just getting used to ridding. Is a hybrid seat like this suitable to be used on a road bike ?
Your LBS's advice should be fairly solid.  Saddles have a denoted usage, but it is not a strict prescription.  For example, my road bike is fitted with a mountain saddle (a Serfas Tegu) and it keeps me quite comfortable for rides of around 4-hours.

Using a hybrid saddle on a road bike is perfectly suitable, however you may require a narrower saddle to accomodate the more aggressive riding position (see Should I use a narrower saddle on my roadbike than I would on my hybrid commuter?); however your LBS has likely taken this into consideration already.

If you are still experiencing discomfort, then you may need to try a different size or a different model.  Saddles are highly personalized options on the bike, so it may take a couple returns before you find the correct one.  The position of the saddle on the bike is another aspect of comfort.  Some riders prefer their saddles at a slight angle, while others prefer it to be level.

Keep in mind with any new saddle there is a break-in period.  Typically you should put several hours of riding time in before making a conclusion--unless it is very uncomfortable right away.  

Also, are you wearing padded shorts?  Padded shorts add a huge amount of comfort--moreso than more heavily padded saddles.  Typically you are better off with a good pair of padded shorts and a fairly firm saddle than you would be with "regular" clothes and a very cushioned saddle.

If you have any concerns go back to your LBS and try to find out who their saddle guru is.  Try to describe the discomfort you're having (e.g. are your legs going numb, do the insides of your sitbones quickly become sore, etc).  They may adjust the position of your saddle or swap the saddle entirely.