How to make maps line up

I'm importing maps to the map layer, but the grids on them don't line up to the grids on the map. I tried resizing the map file but it keeps uploading as the same size on the page.

You should be able to drag the map to resize it freely, so you can manually adjust the image to match (or be close to) the grid.

The easier way is to use a multiple of 70 dpi for the size of your map. Then, you shall be able to snap it on the Roll20 squares, wathever your squares size. You can also resize your map freely, but then it shall be sheer guessing to choose the size. Or you can crop your map to full squares and drag/resize to match the roll20 squares. Graphic assets management is the weakness of Roll20, but it is on the todo list of the devs, I think.

I've found that since Roll20 wants to snap to grid it's best if you crop your maps or map tiles so that the upper left corner of the images is a map grid point. In other words, I had a map that had a white border around it and I couldn't ever get the gridlines on the image to line up with the Roll20 grid. I cropped the image putting a grid corner in the upper left and then it was just a matter of stretching it until the grids lined up. For me, I also had to resize the page so the grid would be big enough to handle the map I imported.