After playing for a while, I notice that the radroaches are getting signifigantly tougher. At first, two low-level dwellers could easily take care of a couple of roaches with their fists, without taking any significant damage. Now I have 4-5 level 20+ dwellers with trained stats and laser pistols, and they often end up at near 50% health after an infestation. Fires seem to scale in a similar way (but aren't really as bad in my experience).
I think the following things are likely the causes, but I haven't been able to confirm this:
- Room size
- Room upgrade level
Some other factors that may be taken into account (but I consider less likely) include:
- Amount of dwellers in the vault
- Room type
- Dwellers' levels
- Time played
What is causing the radroaches to become so powerful?