Usually they ask for refrence, criminal check for the last 5 years... or they used to anyway.
If in your reference form they state they need to know what you've done for the past 5 years (as you stated, you've been living in Spain for the past 8 years), get the Spanish police to release you a document proving you have no criminal record for the past 5 yrs you've been living in Spain.
And after that, it all depends on the base (APT) you've been sent to by Ryanair.
My advice is to, just in case, get both, the Spanish and Irish criminal check. Better safe than sorry (wich means you have the job, are based to so and so APT however the ID officer woke up in a bad mood that morning when your application went thru and decided to deny it and that's you off the roster for a month- seen it, done it, was angry about it...)
Hope this helps