My plan of action - suggestions?

Okay, guys, here's my situation:

I have chemically bright auburn hair. I last had it dyed four weeks ago,
but it was only a touch-up on the roots and a quick refresh for my ends
(at the salon). I am going to experiment with a new box color, L'Oréal
Féria Blush Blonde 94. I am aware that it will not show up much because
color doesn't dye over a darker color, but I'm trying anyway because my
red has faded so it's a bit closer to my root color. My problem is that in
the last four weeks my medium brown roots have grown out about 1/4
inch. I know that if I dyed my hair the light reddish blonde now, my roots
would react with more intensity than my dyed hair.

So, my plan is that I will go to the salon today or tomorrow and get my
roots done the color of my ends. Then, I will use a protein filler to make
my dyed hair less porous. Then, I will dye over my hair with the box
color.

About how much time should I wait in between getting my roots done and
redying my hair? Is this all I should do or does anyone have any
suggestions? Or am I doing this completely wrong?

Thanks in advance, everybody.

Well, I talked to someone earlier who had gone from my exact color to
blush blonde. I also talked to an expert hairstylist who told me that
lighter colors often can be used as a subtle lightener because my hair has
faded quite a bit. (Blame swimming without a cap for a few days, and not
using a color protecting product...) He also told me Feria has a mix of
semi and permanent dyes, so some of the semis wash out while other
permanent shades last. It hasn't faded completely, however, so there's
still a difference between my roots and my dyed hair.

1). My hairdresser has an exact formula for my hair that she uses on my
roots once a month, so when I get them done and my hair cut I'll take a
sample off the floor and use it for my strand test. (I forgot this part)

2).If the color on the strand test comes out as something I like, then I will
use the dye after using a protein filler to even my hair out. (It's been
dyed a ton so it's gotta be porous).

3).l then will dye my whole head blush blonde, but what I am worried
about is even having my whole head the same color and using a protein
filler, will my roots, which have not been as chemically colored as the rest
of my hair, come out brighter?

All in all, I'm using Blush Blonde to acheive a subtly lighter color, not the
color that's on the box (Just because from reading the boards I know that
would never happen with a darker color to start from).

Plus, I have noticed my hair is in much better condition when using the
box dyes than getting it done at a salon (Feria comes with specially
formulated mega conditioner to repair dyed hair whereas they use a
normal conditioner at my salon).

One more thing: what about using olive oil on my hair? Would that even
out my color a little bit between the roots and the dyed color or would it
not do anything? I'm just looking for ways to prepare my hair so that I
don't end up with intense roots like the common problem goes.

Well, I dye my hair occasionally all over (actually have either mom or best
friend to do it, but now best friend's moving...) but leave the roots to the
professionals because I don't think I could get all of my roots. It looks
hard. I've been reading this forum for a while and think it could work.
I'm not expecting the color on the box, just a lighter shade of red but
don't want to ask for a strawberry blonde at the salon for fear they will
bleach it... my hair is individually fine but I do have a lot of it. I always
seem to be losing so much hair (Don't brush often but when I run through
with fingers sometimes a hair will come out in fingers and when using a
ponytail holder) and a guy on my swim team has alopacia and sometimes
I just start freaking out (I'm a hypochondriac) and I don't want bleach to
make it worse!
So I'm really nice to my hair, use leave-in condi every day
and only thermally style it once a week or so. It seems like the longer it
gets, the more weighed down it is, so I'm gonna get a cute shoulder
length bob in a few days. Hope it looks good. It will also be good for my
hair.