I have a 2007 Dodge ram 1500 Sport.
I screwed up & didn't change my rear brake pads before they started eating into the rotors. Is it normal for the rear brake pads to wear out before the front?
My question is; if I changed/installed all, front & rear rotors & pads at the same time time, should I install new front pads while I am now installing new rear rotors & pads. (The front rotors are still smooth & shiny.)

 

If your front pads & rotors are old, you'd might as well change them also. Even on my car that I have now, I recently changed the Front and Rear pads + the rotors all around. They were all due for a change, but then again I drive an AWD Subaru Legacy. I don't want to give you false information on whether or not the rear pads are meant to wear out quicker, so maybe someone else can give their input...

 

Wallet thick with extra unneeded cash for food and mortgage? Change them all. Just need the truck as a reliable daily driver, replace only what is necessary. Brakes are a regular and continuous wear item. It is nice to go all new all round, or just change one ... the practical reality is that there is absolutely no advantage nor benefit to changing any pads or rotors before they reach their end wear points. Just like there is little to no advantage to changing the engine oil early. Now that does not mean to ignore and neglect the brakes. You still have to check them, clean them, and lubricate them 3 times a year.

You indicate the rear pads have scraped up the rear rotors. So replace the rear rotors and pads. Wrt the fronts, check and measure the thickness of the remaining material on the front pads. Less than 4mm, replace them. More than 5mm roll on for another couple months. Neither is it necessary to replace any rotor when replacing pads, assuming the rotors are in fair to good condition.

My mileage which you can use as a gauge: All positions achieve 3 sets of brake pads to one rotor. Rear to front are 2 sets of front brake pads to one set of rear pads. I select good quality material and slotted for the rotors. For pads I select mid grade house brand or Wagner mid grade. I do not select heavy duty, severe duty, or expensive fancy schmancy type pads. Those will eat up rotors regularly. I use the truck as a truck. Town, highway, offload, towing, and hauling.

 

If the front pads are not worn then keep them, but if they're worn out just like the rear then obviously you need to change them. Any chance you know if the front pads are worn out too?

 

It's not normal for the rear pads to wear faster than the front. But, unless you've had the truck since new you wouldn't know when the front or rears have been changed. You could be on your second set of rear pads and third set of front pads, for example.
Take a look at the remaining pad material on your fronts. You will likely need an inspection mirror to get a good look. No need to change the front if there is a lot of pad left.
If you are going to go with performance brake pads, then I recommend changing front and rear pads along with the rear rotors. Reason is that the performance pads will give more bite and it's better to have even friction all around. Performance pads also require a break in, and I prefer to break in all four corners at once. Just a personal preference though.
Also consider changing your brake fluid. It's easier to bleed the fluid with your wheels off. This is assuming you are going to do the brake work yourself.