How do you think the Lannister deal with the workforce for the mines at Casterly Rock? – Do they go in an out every day and live at Lannisport? – Are they quartered at the Rock? – Or are they quartered in barracks outside just outside the Rock?

That’s a great question!

There isn’t an answer in the text, but we do have some idea of how premodern miners lived. 

As mining developed from seasonal labor done between planting and harvest to a specialized craft (especially as increased demand due to population growth and frequent warfare made mining increasingly lucrative), miners tended to live in their own settlements originally built immediately around mine shafts. As H.J Habakkuk puts it: “Whether the mining community formed part of a town or not, it was generally a sort of a state within a state, with laws and regulations of its own…”

This leads me to believe that the miners would probably live in or around the Rock. There’s another reason why this is the case. While miners did have certain legal privileges regarding taxation and their own courts, there were extremely harsh penalties for stealing ore (or more accurately, since lords and kings alike taxed a certain percentage of ore, evading taxes by concealing ore about their persons):

“…If he be attainted of carrying away ore a third time, his right hand shall be pierced by a knife through his palm and pinned to a windlass (1) up to the handle of said knife. There he shall remain until he be dead or shall have freed his hand from the aforesaid knife. And he shall forswear his franchise of the mine and if he have a meer (2) in the mine it shall be forfeit to the lord.“ (source)

If miners regularly commuted to and from Lannisport, with all of its many goldsmiths and merchants, you’d have a wide-open vector for stealing and then processng stolen gold for easy money for any miner looking to make some cash under the table. Given their reputation as tightfisted bastards, I would guess the Lannisters would prefer to have miners live on site or in a mining village where they could more easily “inspect” their workers (strip searches and cavity searches are not uncommon down to the present day in gold and diamond mining) and notice any signs of pilfering. 

Knowing GRRM’s penchant for high romantic fantasy, I would guess the miners live a morlock-like existance deep within the bowels of Casterly Rock, far from sunlight and air, kept under strict discipline by the Masters set above them (literally) under the threat of the cisterns above them been loosed to flood their tunnels and make a second Rains of Castamere. But it’s not all bad. Living close enough to the forges and smelteries would no doubt allow one to laugh at the very idea of winter (or even doubt its very existance), and there’s always the possibility for the strong and clever to work their way up (literally) to better work at the port of the Rock where you’d get to see the sky and smell the salt air, or as a guard or soldier and get to see the world outside.