1) there are no Read-Only security roles, in the standard Dynamics 365 F&O, Every security role in Dynamics needs some license. some security role can be used with a choice of licenses (from many options you can choose any any). Microsoft licensing guide lists the needed license next to each security role.
2) You can create read-only security roles, There are many duties and privileges that can be used with any license, here is an example:
3) You would need at least one license from all possible options for the direct access to the APP (D365 FO), that's what License guide, page number 50 says (last sentence ; provided in next picture)
When it comes to your specific example and you would want to inquire into project transactions, you would have choice to buy any of the following license. [Note: Team Member would not provide you access to all areas in some cases, as in the following example]
Depending upon which area of the system you want to access, license needs can change., When you end up creating a security role, whether it is read-only or not, you can see what license the security role would consume.
I have also seen the examples of custom security roles that consume more than one license (e.g. Finance+Attach Supply Chain)
