At home hair color HELP!?

I have always gotten highlights and the bottom half dark. my roots have grown out about 3", my hair dresser passed away and i havent been to another. So, whats the best way to do at home color? Will my roots be a different color than the rest? Having the bottom half of my hair darker than my natural hair color, how do i avoid making it look worse. HELP! have something coming up fri evening