Final answer:
The literary device present in the line 'my roots are deep in this earth' is a metaphor.
Step-by-step explanation:
The literary device present in the line 'my roots are deep in this earth' is a metaphor. A metaphor is a figure of speech that compares two things by saying they are the same, without using the words 'like' or 'as'. In this line, the speaker is comparing their roots to the deepness of the earth, suggesting a strong and unwavering connection.