I want to get a Drilbur for my W Nuzlocke, and I just realized they only appear in these spots, what do they look like so I can recognize them. Also, should I get a Roggenrola in Wellspring Cave, or go immediately for a Drilbur(Keep in mind, Drilbur's not the only Ground type before Elesa, Sandile is my temporary defense against her, until Chargestone, where I'll get a Drilbur most likely.)
To answer the second part of your question, Roggenrola requires trading to evolve into Gigaltih. Excadrill on the other hand is much easier to get and evolve from Drilbur, so that should be your choice.
In caves, the equivalent of a shaking/bubbling spot is a dust cloud. In water, it looks like a splash or geyser of water. In grass, the grass is shaking.
Roggenrola isn't really that useful, as it can't evolve all the way to Gigalith without trading and doesn't have a very good move pool. Drilbur (eventually Excadrill) is pretty good with a solid attack stat and the great Steel typing, and if you can get an Intimidate Sandile that's great for nuzlockes as it greatly increases your likelihood of surviving hits.