Create a mat ROI for each contour blob?

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How would one create multiple ROI Mat based on a

vector <vector < point >> contours.

I have this function

vector<vector<Point> > MarkCountours(Mat binaryImg)
{
    vector<vector<Point> > contours;
    Mat test = binaryImg.clone();
    vector<Vec4i> hierarchy;
    RNG rng(12345);
    findContours( test, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0) );
    vector<vector<Point> > contours_poly( contours.size() );
    vector<Rect> boundRect( contours.size() );
    vector<Point2f>center( contours.size() );
    vector<float>radius( contours.size() );
    for( int i = 0; i < contours.size(); i++ )
    {
        approxPolyDP( Mat(contours[i]), contours_poly[i], 3, true );
        boundRect[i] = boundingRect( Mat(contours_poly[i]) );
    }
    Mat drawing = Mat::zeros( binaryImg.size(), CV_8UC3 );
    for( int i = 0; i< contours.size(); i++ )
    {
        Scalar color = Scalar(255,0,255);
        drawContours( drawing, contours_poly, i, color, 1, 8, vector<Vec4i>(), 0, Point() );
        rectangle( drawing, boundRect[i].tl(), boundRect[i].br(), color, 2, 8, 0 );
    }

    return contours;
}

This draws rectangle on the binary image, based on contours, but how do i based on those countours create multiple Mat which consist of ROI where the contours are in interest..