Do area rugs and runners have to match?
Keeping this in consideration, do rugs need to match in open floor plan?
It's not impossible to mix rug patterns across an open area. They just can't be so wildly different that they compete. Look for rugs that have a common style, whether they share age, pile height, or texture. This is a bit of a bolder choice, and the easiest way to pull it off is by using Oriental rugs.
In this manner, can you put two different rugs in the same room?
Use the exact same solid or simple rug, TWICE. You can also mix two solid rugs in different colors very easily in the same room. That's just a matter of choosing both in your color palette. The rest of the combinations are trickier.
If your primary furniture, such as a sofa, is a solid color, consider selecting a patterned rug. Match the secondary color in a patterned rug to your sofa. Match the third rug color to your pillows, drapes, wall color or other accents in the room.