Can I just announce that I'm going to tell my roommate to do something instead of asking them?
Why do you want to tell them instead of ask them? Seriously? That sounds quite out of line.
I can't deal with people who can't read between the lines.
It isn't a good idea to tell your roommate to do something instead of asking them politely, because people don't like being bossed around. If you tell your roommate what to do they might come to resent you, which could make living together very uncomfortable.
Well, no one asked for your advice. I was just telling you what I wanted to do.
You are the boss it seems, but isn't that quite nasty to act like you can do anything you want to? Not everyone is adept in reading between the lines you give them, be patient and understanding with others. Otherwise you will have problems in life that can't be resolved.