There is a wonderful parenting series of books called "Love and Logic" by Jim Fay and Foster Cline. Some communities even offer Love & Logic parenting classes. I highly recommend them and the books!
But for more immediate help. I agree with the moms who suggested spending one-on-one time with your son. Go on a weekly "date" with him. During these times you could share with him how frustrated you are with his disrespectful behavior. Point out that you don't talk to him that way, and you expect the same treatment in return.
You must remember your son is not in charge, you are the parent. When he is disrespectful and you tell him to go to his room. If he refuses, simply take his hand and "help" him go there. Let him know he is welcome to come back out as soon as he can speak with you in a respectful tone. Be loving, but be firm.
Also, your hubby needs to back you up on this! Talk with him about it. Sometimes as a SAHM we get worn down during the day, and neglect to even realize we're being disrespected. My hubby would walk in the door and put a stop to any negative behaviors immediately because he would see them with a fresh eye.
It's important to nip this behavior in the bud now, before your son hits his teen years. Good luck!