run("Blobs (25K)");

for (i=0, j=0; i<200 && j<200; i++, j++) {
    makeRectangle(i, j, 8, 8);
    roiManager("Add");
}

roiManager("Select", 199);
borrar= roiManager("count");
for (r=borrar-1; r>2; r--) {    
    roiManager("Select", r);
    roiManager("Delete");
    //roiManager("Deselect"); // slows everything down but works
}