I am going to assume that you are using Windows because you say you have a .dll
I just ran into this same problem that the function qInitResources_resourcefilename cannot be found. This function does indeed exist in the shared library if your library has a .qrc file (check the mapfile). The problem is that this function is not exported and so the linker does not find it while linking the main App. I added the function qInitResources_resourcefilename to the export table of the shared library as follows.
Add a new file to the shared library
export.def
LIBRARY
EXPORTS
qInitResources_resourcefilename
Add the following to your shared library .pro file
QMAKE_LFLAGS += /DEF:\"$${PWD}\\export.def\"
OTHER_FILES += \
export.def
Your solution works around this problem because RmiLib::startResources is included in the export table.
I am using Windows 7, MSVC 2010, Qt 5.2.0