Meilahti Arboretum also features a Rosarium presenting a collection of shrub roses. The Rosarium was started in 1991 and underwent a major renovation along with the park furniture, entrances and gates to the north and south in 2006–2007. Most of the rose varieties were switched during the renovation.

All the roses in the Rosarium are shrub roses. The renovated grounds also include perennials and a pergola for climbing roses and clematis. The shrub roses were selected together with the Finnish Rose Society. The nameplates include the name of the variety in question as well as the year in which it was created (if known).

The Rosarium specialises in European historic roses and Finnish varieties. The plants are grouped according to their historical or botanical background. In addition to familiar and traditional varieties, such as the Valamo Rose and Mustiala Rose, the collection includes many old and unidentified varieties that have been found in different parts of Finland. European historic roses include the French Rose, the Damascus Rose, cabbage roses and moss roses.

The Helsinki chapter of the Finnish Rose Society has helped maintain the Rosarium over the years. The Finnish Rose Society was founded in 1989 to bring together rose enthusiasts, researchers and cultivators. The organisation promotes the cultivation of old and hardy roses, experimenting and using roses, and historical research into roses.

The best time to enjoy a rose scented picnic in the park is summertime between mid-June and mid-August.

’Toukoniitty’, Meilahti Arboretum Riitta Partanen
’Thérèse Bugnet’, Meilahti Arboretum Riitta Partanen
’Schalin 4’, a variety discovered in Finland, Meilahti Arboretum Satu Tegel
’Ritausma’, Meilahti Arboretum Riitta Partanen
’Pikkala’, a variety discovered in Finland, Meilahti Arboretum Satu Tegel
’Lumo’, Meilahti Arboretum Riitta Partanen
’Linnanmäki’, Meilahti Arboretum Riitta Partanen
’Henri Martin’, Meilahti Arboretum Riitta Partanen
’Belle de Crécy’, Gallica family, Meilahti Arboretum Elina Nummi
’Aurora’, Meilahti Arboretum Riitta Partanen