Depois de adicionar as tags do Directory após o IfModule entre as condições e as regras, consegui que a reescrita do URL funcionasse. Aqui está o resultado final do trabalho:
<IfModule mod_rewrite.c>
<Directory "/directory/to/designers/files/">
RewriteEngine On
RewriteCond %{REQUEST_URI} Round_2
RewriteRule ^Round_2/(.*)$ /newBuyer/desktop/$1 [R=301,L]
RewriteCond %{REQUEST_URI} itemList
RewriteRule ^/?(.*)/itemList/(.*)$ /newBuyer/$1/search/$2 [R=301,L]
RewriteCond %{REQUEST_URI} eventDetail
RewriteRule ^/?(.*)/eventDetail/(.*)$ /newBuyer/$1/event/$2 [R=301,L]
</Directory>
</IfModule>
Obrigado