Account Hacked?

I'm not sure who did this, but I checked one day, and I saw in my inventory history that my most valuable tf2 items were traded to a random account. I have no rememberance of making such a trade, and I never share my password to anyone.
http://steamcommunity.com/id/ros_/inventoryhistory/
Help please?
I think steam fixes these types of things and restores items, but I'm not sure how to do that

You should try submitting a ticket to steam, they sometimes do restore items/games but you will need strong proof.

Well first off, only the owner of the account can see the inv history. If you wanted us to see what had happened, you would need to screenshot your inv history and upload it onto imigur or the like.
If you have been hijacked, you can contact Steam Support, and if sufficient evidence is provided, they will return your items. Did you have Steamguard disabled? Normally you can't hijack a Steamguard protected account without both the account password and the email address and password.

Hope you get your items back.

It is possible you accidentally used some phishing link and inputted your login/pass.

You need to submit a ticket to Valve, be aware they only restore hijacked items once or something like that, so weight up what you lost.