Are there other user-role-editor-ru_Ru translation files at the wp-content/languages/plugins before you moved there files from User Role Editor Pro /lang folder?
Free version of User Role Editor does not include translation files into its installation package. WordPress downloads them from the centralized resource:
and places exactly to wp-content/languages/plugins folder.
Both free and Pro version uses the same text domain. So WordPress can use translation files from a free version instead of those included into the Pro version folder.
Will valid translation be shown if you remove URE translation files from wp-content/languages/plugins folder?