Hello, are you putting the lawn completely to the trunk?, or are you going to keep the magnolia to a certain size ? and by doing so you could create a circular bed, which could be underplanted with some spring bulbs, eg snowdrops, crocus, dwarf narcissi, and some autumn crocus, cyclamen look great under magnolia, if you opt for lawn under the magnolia, then i find the grass becomes very tired and sparse, but if you do then try and keep it free of leaf/flower drop, if you go for option 1 then the odd raised root cut off will not be a problem so long as you do it now rather than at the back end,julien.