Roy's biggest flaw is his defensive play. Practice doing Up B out of shield / grounded Up B, it's an underrated move in neutral and the armor frames let you scape some multihit moves and counter them, even FSmashes and strong attacks.
As a Roy player you need to know how to do the Fox Trot cancelling (Or extended dash dancing) and master it, I think his best deffense is running away and dash dancing.
When you are not attacking, just roll away, dash dance and wait for the oppening. To deal with projectiles, run and shield, he is fast enought to punish most projectiles. He needs to pressure the opponent and stay evasive to win neutral.
But yeah I think Lucas is not a good matchup for Roy, Ness is a terrible one so...