Hi, I have just bought a Hardrock Specialized mountain bike and am wondering if this will be ok for road use as well as rougher terrain? I will be using the bike on tarmac a fair bit more than on the rough.
Which Hardrock? They make about 5 different ones?
http://www.specialized.com/us/en/bikes/mountain/hardrock
If it has a lock-out front fork, lock it out on pavement & smooth trails. Install a set of Kenda Kross tires if you'll be mostly on the streets.
http://www.amazon.co.uk/Kenda-Kross-Plus-Mountain-Bike/dp/B004SG97VU/ref=sr_1_1?s=sports&ie=UTF8&qid=1359896724&sr=1-1
It will be harder work than a road cycle, the knobbly off road tyres and suspension are not efficient on smooth, hard, surfaces.
If you can lock the forks it will help, but if you intend to ride only on roads then you should think about changing the cycle for a more suitable one.
Another alternative might be to fit road tyres, that will improve the ride, but you'll still have off road gearing, and the riding position won't be correct for riding at on - road speeds.
It really depends on how much you intend to ride off road, and how rough that off road riding will be.
It will be OK, but you may want to lock out the suspension if possible and swap tyres to something skinnier and slicker than your off-roads to reduce rolling resistance.