I think you need to say where you are as this has an effect on the timings.

When you do the weedkilling, you need to really kill the weeds off including the roots, hence systemic weedkiller like glyphosate. Rotovating before the roots are really dead is an excellent way of progating perennial and difficult weeds. Whether it is too late in the season or just right to do the killing depends upon where you live - you need stuff to be in growth, and you need enough top growth for the plants to take in the systemic weedkiller through the leaves, so your cutting it all back to ground level may have been counter-productive unless it is still all growing strongly in your climate. One application often isn't enough, a second application to kill what comes back may be required. And there will always be seeds of annuals (which is another reason to be wary of a deep rotovation bringing lots of dormant seeds up). Some particularly persistant stuff, brambles or whatever, needs particular attention as a couple of applications of glyphosate doesn't suffice.