What are other ways one can say that have the same meaning as, "I'm rooting for you?"
NOTE: I've just seen the (recent) duplicate of this question, which seems to have been the motivation for putting a bounty on this question. My answer attempts to cover all the most plausible scenarios in which one might use the phrase, but in the context of the other question, it is the third section that's most relevant here.
I think it depends a lot on the context, and in particular whether the speaker is in a position to exert some influence the outcome, or only to hope for the best.
In a position to influence the outcome
If you were heading into a meeting where someone was going to be selected for a job, for instance, and you were going to be part of the discussion, you might say
I'm right behind you
You've got my vote
I've got your back
If you'll be avidly watching but can't hope to have any significant influence (e.g., sports) then you might try
I'll be with you every step of the way
(perhaps a careless promise if it's a marathon...) or
I'll be cheering you on
Away from the action
If you can't even watch, but want to offer what moral support you can, the language again changes. Suppose you were sending someone in for a heart bypass; you could say
I'll be thinking of you
You're in my thoughts and prayers
or (if you want to get really sentimental and maybe even slightly creepy)
I'll be holding you in my heart
I've heard I'm rooting for you used in all these contexts. The point is that it's really a vague expression of some kind of unspecified support, and so how it gets cashed out will depend on the nature of the support you can offer.
"I'm rooting for you", in this context, root would be defined as follows:
root /rut or, sometimes, rʊt/ [objectless verb] (1) to encourage a team or contestant by cheering or applauding enthusiastically (2) to lend moral support. Origin: 1885-90, Americanism; perhaps variant of rout /raʊt, rut/ [verb] to bellow, roar [noun] a bellow. Origin: 1250-1300; Middle English rowten < Old Norse rauta to bellow; akin to Latin rudere (ablative singular of rūdus).
Therefore, some alternative sentences would be:
- "You'll be getting standing ovations from me."
- "I've got your back! Go get 'em!"
- "I'll be there to support you."
- "I'm cheering for you."
Root for - phrasal verb - definitions from diferente sources:
- to show support for someone who is in a competition or who is doing something difficult.
- to wish the success of or lend support to someone or something.
- take sides with; align oneself with; show strong sympathy for.
- to support someone in a game, competition, etc
- Support or hope for the success of (a person or group entering a contest or undertaking a challenge)
“I’m sure you'll win. Everyone's rooting for you.”
"We all rooted for the home team."
"Most of the crowd were rooting for the home team."
As for your question, in addition to Thursagen's suggestions ("I'm supporting you", "I'll cheer for you" and "I'll barrack for you") and several others cited in the comments, I've found the following:
I'm siding with you.
I'm pulling for you.
In a sports context, however, "I'll cheer for you" and "I'm supporting you" sound like better choices.
You can use different expressions depending on the situation. Here are some of them:
- I am right behind you.
- You've got my vote.
- I'll be with you at every step.
- I'll be cheering for you.
- I'll be thinking of you.
- You are in my thoughts and prayers.
Look here for the explanation.