Dear @joheet 

Thank you for your question. Indeed, sitting for long hours and working is one of the common causes why people develop a stiff and sore back. From the symptoms that you have described, it appears like that pain is limited to the lower back without any radiation of pain or an 'electric' sensation running through the legs, which is good. That means that it is less likely that there is any form of nerve impingement. The fact that you get temporary relief from standing, walking and foam rolling also clues in to the fact that a large component of your pain is muscular in origin.

While it is going to be the new norm that a significant number of people will be working from home, I think it is good to consider augmenting our home environment and our practices to suit this 'new norm'. First of all, I would advise you to take breaks every 1-2 hours or so of sitting to do gentle stretching to 'loosen' your back muscles. Injuries to the back usually happen when the spine is stiff. Sudden movement of a stiff spine often causes injury which results in pain. Pain that leads to even more stiffness. Therefore, in order to break this vicious cycle, regular stretching is useful. You can find some simple stretching exercises on the Internet. Regular yoga  or pilates classes may be useful to improve flexibility too, if you can afford the time. Once you have incorporated the regular stretching to your routine, you can then transit to adding further exercises to strengthen your back muscles. 

Apart from these exercises, having good back care habits are important. For example, bending the knees to lift objects from the floor rather than bending the back. Sitting with a good posture while typing. Having a good back support on your chair.

I hope these tips will be useful for you!