First off, welcome to the Forums.
Roketas are nice bikes, but I haven't drove on a 250 very much.
I use standard Castrol H.M. oil. There is a "Scoot Specific" oil but its way expensive, and doesn't do much difference, in my opinion.
For the filter, every oil change, just scrub out the screen and threads with a toothbrush.
Have never seen a magnet in one, but that could be helpful in gathering any metal flakes... Except aluminum..
I recommend doing just on and off 'city driving' for break in. Stop and go, not holding full throttle but getting there anyways. Also, change your oil at the first 200, 500, and 1,000 miles. Then just every 2,000 after that.
250cc bike don't really need much in the way of HP parts. But an unrestricted CDI from NCY is always a help Changing the air box to a more opened pipe or uni helps breath nicely, too. And a Hot Spark Coil (usually red wire) makes sure you have a solid strong spark every time.