My roommate ate my garri again and I'm supposed to just smile?

I came back from evening class today, tired and hungry. My budget for the week is already tight, 2,500 naira per day for everything. I had planned my meals, knew exactly what I was eating tonight. Opened my food flask and my garri was almost finished. My roommate, the same guy who borrowed my power bank last week and returned it dead, had helped himself again.

I confronted him and he just laughed, said 'oga na small garri you dey cry for?' Like the 500 naira I spent on that garri is nothing to him. These hostel people will stress you. They think because you are quiet you are a pushover. I am tired of being the nice guy who gets used. My mother always says 'onye e mesala ibe ya, ya emesala onwe ya' but when does it end?

I am thinking of keeping my food in a padlocked box. Is that too extreme? Or should I just start eating outside and let him starve?