You can't mix interfaces, unless the product says so, with drivers support, but generally applies to high end interface of the same brand / model.
If you're mostly recording audio live, check out the affordable Alesis Multimix - since it's a mixer plus interface, there is no latency at all, even if you set the buffer higher.
Depends on how many mic pre amps you need, the Focusrite 6 ins may fit your bill too.
Go for slightly more channels than your current max.
edit : btw, the Roland Quad, out of the box, is only a 2 channel interface, unless you have another spdif audio device for 2 more inputs.