Since 31st of January 2012 The Republic of Bulgaria apply a visa-free system for holders of valid Schengen visas until the date of full accession to the Schengen zone. The holders of Schengen visas have the right to enter and reside in the Republic of Bulgaria for a period of validity of their Schengen visas and permitted duration of stay, but no more than three months in any sixth-month period from the date of first entry and without Bulgarian short-stay visa.
Since 31st of January 2012 The Republic of Bulgaria apply a visa-free system for holders of valid Schengen visas until the date of full accession to the Schengen zone. The holders of Schengen visas have the right to enter and reside in the Republic of Bulgaria for a period of validity of their Schengen visas and permitted duration of stay, but no more than three months in any sixth-month period from the date of first entry and without Bulgarian short-stay visa.
http://www.bulgarianembassy-london.org/index.php?option=com_content&task=view&id=90&Itemid=158
你持有意大利的居留的话其实就算是temporary residence in schengen region,所以是可以凭借签证+居留进入保加利亚的。(再检查一下你的签证上是否有schengen标识啥的吧~)
如果还不放心的话可以写个邮件去确认一下~