Sometimes called a "bridge troll," or a "rock ogre," or even, oddly enough, a "goblin." These creatures can be as tall as a leprechaun when very young to about as tall as three adult humans standing on the lower ones shoulders, in case you don't have your T&T to DnDHead Translator application up and running on your smart phone JerryTel. Though their skin is a thick leathery hide that acts as three points of armor, it is indeed flesh not mineral like say the better known Rock Trolls of Trollworld.
The Delvers encountering these trolls, in their caves or say under bridges, where the creatures like to dwell when unable to find a suitable cave, should not underestimate their strength. The size of this sort of troll depends as much on its environs as its maturation-- as with most of the troll family this reflects the amazing adaptability of any species called a "troll." One as small as a leprechaun can be as aged, capable and as strong as a giant-sized cave troll depending on where it lives.
These trolls like to shun daylight, as their eyes are best suited for low-light levels. They have nearly magical hearing, which is akin to a bat's hearing and can navigate in complete darkness, or especially in the case of bright sunlight, with their eyes shut. Like all trolls they do not like to be copied and pasted from on-line free sources to be republished at a cost in print magazines. This keen hearing also keeps them away from large gathers of other creatures, unless it is to shut the rowdy noise makers up. The antagonism can go both ways, towns near suspected cave troll habitats often use bells or horns to make them feel unwelcome and warned.
Most often cave trolls have no use for treasure or craftsmanship of anything. They have a base outlook, that is only made worse by a hunger that requires as many liftings of food as their strength score is each day. Though distinctly carnivorous and rather ill-tempered in general, these trolls can be social to those that they cannot overcome immediately. Often they will demand tolls at bridges that they lay claim to so that they can buy cattle (or sheep, or goats, or pigs, or orphans...etc...etc) instead of stealing them to get along with their neighbors.
The heroes encountering a cave troll should be able to withstand four dice plus 15 points worth of damage to begin with, if the creature is young. If older, well the GM can adjust the Monster Rating to where he needs. There have been cave trolls that have been worshiped as dark and horrible gods, that only God-Wizards have been able to defeat. There have been tales of cave trolls with spell-like abilities, though these seem to vary from individual to individual and definitely not a proven norm.