It is clear from the Shulhan Aruch’s discussion about the properties of halachic "bread" (Orah Haim 168) that if bread was baked with a sweetening agent, such as sugar or honey, and the sweet flavor is easily discernible when eating the bread, then one does not recite "Ha’mosi" over such bread. Bread with a noticeably sweet flavor, according to the Shulhan Aruch, falls under the category of "Pat Ha’ba’a Be’kisnin," and thus one recites "Mezonot" and "Al Ha’mihya" over such bread, instead of "Ha’mosi" and Birkat Ha’mazon.
Rabbi Moshe Ha’levi (Israel, 1961-2000), in his Birkat Hashem, contends that even the Shulhan Aruch would agree that if one uses sweet bread in the way ordinary bread is used, then the bread requires "Ha’mosi." In his view, "Pat Ha’ba’a Be’kisnin" requires "Mezonot" instead of "Ha’mosi" because such products are eaten as snacks, and not as a meal. As such, even if one eats sweet bread, he recites "Ha’mosi" if he eats this product the way regular bread is ordinarily eaten.
However, Hacham David Yosef (contemporary), in his Halacha Berura, disagrees with this ruling, and refutes the proofs which Rabbi Moshe Ha’levi brought to support his position. According to Hacham David, anytime one eats sweet bread whose sweet flavor is easily discernible, the Beracha is "Mezonot," and not "Ha’mosi," even if he eats this bread as ordinary bread.
Therefore, when preparing or purchasing bread for the Shabbat meals, one must ensure not to prepare or purchase bread that has a readily discernible sweet flavor.
However, Hacham David emphasizes that this Halacha pertains only to bread whose sweet flavor is easily discernible. Some companies produce bread with fruit juice instead of water, and label the product "Mezonot rolls" because the bread is considered sweetened. Hacham David writes (listen to audio recording for precise citation) that these rolls are, generally speaking, not discernibly sweet, and so they require "Ha’mosi" and Birkat Ha’mazon just like ordinary bread.
This is especially true for Ashkenazim, who follow a different opinion, and recite "Ha’mosi" even over noticeably sweet bread, unless the sweetener constitutes the majority of the product. According to Ashkenazic custom, one certainly recites "Ha’mosi" over so-called "Mezonot rolls," and even over discernibly sweet bread.
Summary: According to Sephardic custom, bread baked with sugar, honey or other sweetening agents, and thus has a discernibly sweet taste, is not considered Halachic "bread," and thus one recites "Mezonot" and "Al Ha’mihya" over this bread, instead of "Ha’mosi" and Birkat Ha’mazon. Such bread should therefore not be used for "Ha’mosi" at the Shabbat meals. However, if the bread does not have a discernibly sweet taste, then even if it is baked with sweetening ingredients, such as fruit juice, it is considered bread and requires "Ha’mosi" and Birkat Ha’mazon like ordinary bread. Therefore, so-called "Mezonot rolls" which were baked with fruit juice require "Ha’mosi" and Birkat Ha’mazon, unless they have a discernibly sweet flavor.