Using 433 MHz modules to transmit independent pair of codes like in car-key application is possible within a small area.
In a room, such transmission may not work if the pairs of modules operate in the same RF channel. Due to interference transmission will be interrupted.
You can arrange that data in one channel are transmitted one block after another , then two pairs of systems can work in a room. This is called a time multiplexing.
If you can find the transmitter-receiver pairs using different channels in the 433 MHz band, it may work, too. In a small room I would, however, the time multiplexing much better.