How long should I leave hair dye in?

This is the third time trying to dye my hair. My hair is naturally dark DARK black. The first time I dyed my hair I went to dark brown just because it was the first time and I didn't want there to be a big difference . It turned out okay I guess, pretty much just added high lights to y hair eve though I put the dye all in my hair. This time I left it in for 25 minutes. The second time I tried to go burgundy, though I didn't use developer so I guess that might be why it didn't have any affect. I also left that one in for 30 minutes. Now, I just tried to dye my hair again a burgundy color and I left it in for 30 minutes, using developer, and it only died my roots pretty much. I left it in for 30 minutes but I noticed that I applied it to the roots 15 minutes before applying it t the rest of my hair, which is wasn't wasn't dyed. The next time should I leave the dye in my hair for 45 minutes or is that too much? Because otherwise I guess I should just go to a saloon to get my hair dyed now.