I color my hair with henna. Because it's a permanent natural conditioning dye, and I mix conditioner into the henna itself to make it easier to rinse out, I don't do anything special afterwards. I plan on using henna every time I retwist my hair (which at the rate I'm going, will be every week).
Now, when I used to use the chemical dyes (Feria Professional Permanent) - I would deep condition my hair immeadiately after dying it, and for the first month, I would DC every week. After the first month, I just DC'd with a color preserving treatment (I think it was by Ion) every month. I never had a big issue with roots, so I would dye my hair whenever I felt like changing the color - which would usually be about every SIX months or so.
My hair hates protien treatments, so, I never used them.