These things are always tricky business.
Hours after the conclusion of the 2015 NFL draft, there's an insatible desire to acquire information regarding players that weren't selected in the NFL draft. At the end of the day, we had 16 signings but the team only confirmed 11 on Friday -- which makes sense considering that the roster limit had reached 76, which included draft picks -- need to leave space for tryout players that make an impression.
There are other reasons why no announcement was made on some players: 1) negotiations are ongoing 2) the player hasn't arrived in Cincinnati to sign the deal (the Bengals do NOT confirm a signing unless ink is on paper) 3) the "signings" were actually tryouts 4) another team swung into action and offered that player a better deal.
The five players that Cincinnati didn't sign (as of this posting):
+ University of Miami QB Ryan Williams: Our source was the player tweet, as well as a tweet from his representatives. It was also confirmed with the Cincinnati Enquirer. It wouldn't be surprising if Williams is eventually announced.
+ Tennessee-Martin LB Tony Bell: Source was head coach Jason Simpson, who sent the tweet after the NFL draft. It's possible that he could be a tryout.
+ Oregon SS Erick Dargan: Source was the Oregonian (the major newspaper out of Portland). According to the story, Dargan confirmed with the newspaper that he signed with the Bengals. According to the story, Dargan had been talking with "five or six" teams before landing in Cincinnati. Was there an issue with negotiations? Did another team make another offer after the report?
Duke defensive lineman Dezmond Johnson: Source was Fox Sports, as well as the Duke's football twitter page.