If you consider making a bed in the lawn, you should remove the turf, otherwise the buried grass will just regrow. Beds in the Lawn
You might want to spread your left over garden compost over your beds, it will improve the soil for next spring greatly. Improve your Soil for Spring
Remember to cover up your rose bushes for the winter, apply a handful of bone meal on the rose bed for good measure. Take Care of Your Rose Bushes