Read the directions on the product label. Keep in mind that that hose end sprayer can never again be used for anything else.

I would advise against using a hose end sprayer for Roundup. Not only is it difficult to get a precise ratio of concentrate to water and difficult to aim carefully, it is major overkill for applying this herbicide. Only a very small amount of spray material is needed on weed leaf surfaces to work. A hose end sprayer is best suited for materials that don't need precise percentages and need to be applied through a heavy drenching spray.

A hose end sprayer is totally the wrong tool to use when applying Roundup. Period. I assure you that you'll not find directions for this type of application on the label.

Best to use a small pump-up sprayer. One that you can deliver the herbicide under enough pressure to emit the fine mist desired for the effective use of Roundup.