Kamakura is a historic town beloved by some renowned Japanese authors such as a Nobel Laureate Kawabata Yasunari, and the Kamakura Museum of Literature exhibits manuscripts by those writers and their belongings. This museum building nestled among trees is the former residence Earl Maeda, has a rose garden with 250 rose trees in 200 varieties. 

Rose Festival at Kamakura Museum of Literature
 鎌倉文学館バラまつり

Between mid-May and  early June

Location:
 Kamakura Museum of Literature, Kamakura City, Kanagawa Prefecture

Opening hours:
March to September 9:00 - 17:00 (entrance closed at 16:30) 
October to February: 9:00 - 16:30 (entrance closed at 16:00) 

Closed on Mondays (Opens if Monday falls on a national holiday)
To find other closing days, see their official website.

Admission fee: 400 JPY

Note:
*In this museum, visitors are not allowed to use anything to write with (pen, pensile etc.)
*In the museum, no photographing is allowed.
*In the rose garden, visitors are not allowed to use camera stands and selfie sticks as the path is narrow.

For details, check the info on their official website

Getting there
7 min walk from Yuigahama Staton 由比ヶ浜駅 on the Enoden Street Car 江ノ島電鉄

Official website (Japanese website)
http://www.kamakurabungaku.com/
http://kamakurabungaku.com/event/index.html

Related article on digi-joho TOKYO
Kamakura, a historical town in Kanagawa