“One of my earrings fell off, it rolled under the stove,” is a RUN ON sentence. You can tell by the comma splice (which separates two different, yet complete, thoughts incorrectly through using only commas). You can also tell because it holds two complete sentences without the proper conjunction or punctuation needed to connect them.
To fix a run on, you must use a conjunction (and, but, for, yet, not, or, so) between the two complete thoughts or place a period between them.
Example: one of my earrings fell off. It rolled under the stove.
OR
Example: One of my earrings fell off and it rolled under the stove.