I'm not sure what you want to accomplish, but most of the IMAQ ROI VIs have an ROI descriptor parameter that contains the coordinates of an ROI. You could use this input to set the location of your ROI where you desire. If this does not help, please be more specific about what you are trying to do.
i want to draw a roi on a big image.. and i want to draw it mostly on the right lower corner.. so i would like it when it would always display the right lower corner, not the left upper
You can use zoom to control the portion of the image that is displayed in a window. If you always want the lower right corner to be displayed, you can calculate the center of the displayed image based on image size, window size, and zoom factor.