As a Soldier in the United States Army you have the right to:
1. Observe the tenants of your Religion (a sincerely held belief), or observe no religion at all. (US Constitution Amendment 1; DoDI 1300.17) This means that not only do you have the right to beliefs, but to perform associated acts such as assembly, speaking (e.g. sermons, prayers, worship), and to NOT perform certain acts (e.g. being forced to worship, or affirm disbeliefs).
*NOTE: IAW the Religious Freedom Restoration Act (RFRA), the Army may issue an order that "bans an aspect of religious observance or practice, compels an act inconsistent with that observance or practice, or substantially pressures the adherent to modify such observance or practice" but only if such an order is of "compelling government interest" (e.g. defending a base against an enemy attack that occurs on a holy day), and uses the "least restrictive means" to accomplish that interest. The Chaplain can assist you if there is a dispute over such issues. It is a Chaplains sworn duty to support all Soldiers, regardless of ideology, in defense of these rights.
*NOTE: The Army defines "religion" as "professing a set of beliefs concerning the cause, nature, and purpose of the universe, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs” (ATP 1-05.04, 2-33)
2. Receive equal treatment in all regards without regard to Religion on and off post, during duty and non-duty hours in all work, living, and recreational environments . (AR 600-20, 6–2). Soldiers will not be accessed, classified, trained, assigned, promoted, or otherwise managed on the basis of religion. This includes treating a person unfavorably because of sincerely held religious, ethical, or moral beliefs, or a connection to a religious group, including the beliefs and connections of their spouse. (AR 690-12, 1-6, D-1)
3. Express your faith, to include evangelism. (DoDI 1300.17 1.2./AR 600-20). Despite popular opinion there is NO regulation against proselytization or evangelism or public conversation about your faith. In 2006 there was a CENTCOM general order issued to those assigned to "Multi National Corps- Iraq" which forbade proselytization. Even this antiquated document was open to interpretation and had virtually no clarification on a minor part of a very long list of expected behaviors. It should be noted, however, that anything deemed to degrade the mission is subject to command authority which allows for a subjective tension with the anti-discrimination laws above.
DA PAM 165-19 2-6 states that "Army professionals [which includes all Soldiers] have a right to religious expression [not just to hold beliefs, but outwardly demonstrate] in the workplace [on federal property, in or out of uniform]," but that is not a license to deviate from the Army Ethic (enduring written codes of ethics) or to harass Soldiers since. AR 600-20 Defines harassment to include "unwelcome conduct based on race, color, religion, sex (including gender identity), national origin, or sexual orientation." Note that "unwelcome conduct" is not defined. Note also, however, that protection as here defined is equally provided to those expressing an opinion, and those hearing an opinion expressed.