Roots frequently accumulate next to container walls. To help keep them cool in the summer try double potting. Put potting soil between the pots as an insulator. If you use decorative ceramic containers, be sure they have drainage holes, otherwise use them as a decorative cover to hide a well draining but unattractive container. Plant roots function like a water pump, taking minerals and nutrients to every part of the plant.
Roots die in both situations.
Add water to container plants until water flows out the bottom. If saucers are used, be sure to empty them. Otherwise you can drown your plants. When the soil stays soggy, the oxygen is driven out of the soil pores, the roots suffocate and rot, and the plant dies. Of course, different plants have different needs.