I have a slight fret-buzz (starting at about 4th fret), I have an Ibanez GSA60, with a SAT10 tremolo.
Now I was wondering, If I got myself height adjustable saddles, wouldn't that solve my problem? also, how do I know if the saddles will fit my guitar, and which saddles would you recommend?

The saddles on it are height adjustable, you shouldn't need new ones.
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
What? 14 people haven't been screaming adjust the truss rod???

OK I couldn't resist. but in this case it sounds like a good time to check the neck relief, and see if it actually has a hump in the neck, meaning truss rod adjustment. The neck should bow slightly away from the strings in the middle, to allow them to vibrate without buzzing against the frets.

I would check it before changing saddles, although I would change them anyway just to be able to adjust the action.

Put a capo on the 1st fret, fret it at the 12th to 14th. Check at about the 7th fret or so and see how much space is between the bottom of the E strings and the top of the fret. Proper neck relief should get you somewhere around .010 - .015". To get more neck relief, loosen the truss rod (counter clockwise) 1/4 turn and no more, let it sit overnight to settle in.

After letting it sit overnight if it still does not have enough do the same again, never more than 1/4 turn at a time and always let is settle in overnight. Usually shouldn't take more than one adjustment, but if it has enough to start fret buzz at the 4th fret it might need 1/2 turn total.
Hmmm...I wonder what this button does...