MT does not currently have an API available, so no plug-ins. We plan to do that in the future.
ROC - Rate of Change - What would Yesterday's ROC be? Change from previous close? that is already there - the CHANGE and CHANGE % column. As for other indicators, adding them as columns would mean they have to be computed in real-time for all symbols in the portfolio being viewed, which can be expensive (as far as CPU usage). We do plan doing that at some point, but right now it is low priority