Pipplin - I wouldn't concentrate too much on "condition" as such with your hair, presuming you aren't doing anything out of the ordinary to it. If its not overfried, or overdyed, in terms of styling/colouring, I would go with a good bog standard shampoo and conditioner which isn't too heavy and offers some heat protection.
Then, if you want lovely sleek healthy looking well conditioned hair, you need to learn to style it.
Your hair looks the way it is because its naturally that way. (Assuming you are not doing anything terrible to it anyway).
If you have that kind of hair, you either need to learn to blowdry it properly to tame the frizz that makes it look unhealthy, or perhaps try an Instyler (QVC sell them for risk free trying, JML too, or try the Babyliss version which is the "big hair" which is essentially a rotating round brush styler)
Your roots probably seem greasy because you simply have fine hair. Learn to love dry shampoos and the less you wash the less you need to.
I'm no professional but go to a decent hairdresser and get them to assess your hair - they can do this if washing and drying it - and cutting it - get them to confirm that there is (probably) nothing essentially wrong with the way you are treating it in terms of maintenance, but it needs taming with styling.
My hair looks and seems incredibly healthy even though I dye it and bleach it (highlights anyway) and whilst I look after it with products, the reason it looks so healthy is its simply sleek, straight, well behaved hair, I'm sure of it.