The message from the coder module is pretty much nonsense. The text of the error message doesn't really explain the problem.
You cannot pass variables into the t() function like that (check the docs in the link It specifically says that).
The reason is users submitting translations can't possibly know what is in that variable so it cannot be translated.
Also, you don't need to run through check_plain() if you use t() correctly as it will do that for you (check out the different replacement patterns you can use and what they do in the drupal 6 version of the docs for the t() function).
You should do it like this:
'#title' => t('Role Limit (@value)', array('@value' => $value)),