Rogation days are traditionally days of prayer (with the litany of the saints being sung) and fasting.
The custom of Rogation Day processions, including the singing of the litany of the saints, in the lead up to the Feast of the Ascension ('the lesser litanies') has largely been lost these days. The picture above is of the traditional blessing of the fields on these days (appropriate at this time of the year if you are in the Northern Hemisphere at least!), taken in Kent in 1967. The other common practice was the "beating the bounds", in which a procession would proceed around the boundary of the parish and pray for its protection in the forthcoming year.