How to you mean with scrypt?
And what is ROI? Im just a beginner :/
Dont get fooled. You dont need to mine Litecoin aka Scryptcoins. Just go for NeoScrypt or X11 ones. 3 Cards would be better but 1 is also ok. - Take a look at Feathercoin, switched recently to NeoScrypt which is GPU friendly.
If you got any questions, head over to the forum: forum.feathercoin.com
Regards,
ChekaZ