Read this - read it in detail. You need to comply with it - to the letter.
https://www.ryanair.com/gb/en/useful...bin-bag-policy
Ryanair roller bag size limit is smaller than many other airlines. Do not assume that "this is what I do with other airlines" has any relevance to Ryanair.
If you do not hold an EU passport, also read up about their document check process which you must complete before attempting to drop bags,