Eep, forgot about that. Natural Cure is Ability 1 according to Smogon (which I believe lists them in the correct order), so while your PID is still valid and legal, anyone poking into the file can see that it's not 100% legit.
Col/XD pokémon have the same odds of being shiny as any pokémon from the handheld games - namely 1/8192. I'm not sure when the shinyness of a Shadow Pokémon is determined, but that's moot in this case.
I had a go at making it shiny. Problem is, getting those exact IVs to be shiny is difficult, and since you've got Hidden Power I assume you picked them out for a specific type and power, and so you don't want to change them. From there it becomes a trial-and-error guessing game - change your ID or SID to something else, run the numbers through PID/IV Checker and hope that one of the results has your specific IVs. And the search process can take upwards of ten minutes to run...
Same deal with fixing the Ability I'm afraid - that particular combination of IVs won't generate a Female Timid Ability 1 Roserade, and it won't generate any of the other natures that you'd find beneficial (namely ones that increase Speed or Sp. Atk) either. Changing the IVs is the only way to get around it, and even that isn't foolproof.