diff --git a/rock.osdeps b/rock.osdeps
index e5d8544..ccd0412 100644
--- a/rock.osdeps
+++ b/rock.osdeps
@@ -39,12 +39,13 @@ binding_of_caller:
 activesupport:
   ubuntu: ruby-activesupport
   debian: ruby-activesupport
+  gentoo: dev-ruby/activesupport
   default:
     gem: activesupport
 
 eigen3:
     debian, ubuntu: libeigen3-dev
-    gentoo: dev-cpp/eigen
+    gentoo: dev-cpp/eigen:3
     fedora: eigen3-devel
     arch,manjarolinux: eigen3
     darwin: eigen
@@ -56,6 +57,7 @@ pkg-config:
     fedora,opensuse: pkg-config
     arch,manjarolinux: pkg-config
     darwin: pkg-config
+    gentoo: dev-util/pkgconf
 
 webgen:
     gem:
@@ -105,7 +107,9 @@ freeglut3:
 
 osg:
     debian,ubuntu: libopenscenegraph-dev
-    gentoo: dev-games/openscenegraph
+    gentoo:
+        - dev-games/openscenegraph
+        - dev-games/openscenegraph-qt
     fedora: OpenSceneGraph-devel
     macos-brew: open-scene-graph
     macos-port: OpenSceneGraph
@@ -123,8 +127,8 @@ qt4:
     # QMake is needed for the CMake macro for Qt4
     debian,ubuntu: [libqt4-dev, qt4-qmake]
     gentoo:
-        - dev-qt/qtcore
-        - dev-qt/qtgui
+        - dev-qt/qtcore:4
+        - dev-qt/qtgui:4
     fedora,opensuse: qt-devel
     macos-brew: qt4
     macos-port: qt4-mac
@@ -132,7 +136,7 @@ qt4:
 
 qt4-opengl:
     debian,ubuntu: libqt4-opengl-dev
-    gentoo: dev-qt/qtopengl
+    gentoo: dev-qt/qtopengl:4
     fedora,opensuse: qt-devel
     macos-brew: qt4
     macos-port: qt4-mac
@@ -146,7 +150,7 @@ qt4-webkit:
 
 qt-designer:
     debian,ubuntu: qt4-designer
-    gentoo: x11-libs/qt-gui
+    gentoo: dev-qt/designer:4
     fedora,opensuse: qt-devel
     macos-brew: qt4
     macos-port: qt4-mac
@@ -163,6 +167,9 @@ opencv:
     macos-port: opencv
     opensuse: opencv-devel
 
+opencv4:
+    gentoo: =media-libs/opencv-4*
+
 jpeg:
     debian,ubuntu: libjpeg-dev
     fedora: libjpeg-turbo-devel
@@ -180,6 +187,7 @@ poco:
     debian,ubuntu: libpoco-dev
     macos-brew: poco
     macos-port: poco
+    gentoo: dev-libs/poco
 
 faye-websocket: gem
 rack-cors: gem
@@ -197,6 +205,7 @@ thor:
     ubuntu:
         precise: gem
         default: ruby-thor
+    gentoo: dev-ruby/thor
     default: gem
 
 qtruby:
@@ -244,8 +253,10 @@ rbtrace: gem
 
 google-test:
     debian,ubuntu: libgtest-dev
+    gentoo: dev-cpp/gtest
 google-mock:
     debian,ubuntu: google-mock
+    gentoo: dev-cpp/gtest
 
 # For backward compatibility with the previous definition in the 'rock' package
 # set
@@ -277,12 +288,14 @@ cdbs:
 
 cmake:
     debian,ubuntu: cmake
+    gentoo: dev-util/cmake
 
 cowbuilder:
     debian,ubuntu: cowbuilder
 
 curl:
     debian,ubuntu: curl
+    gentoo: net-misc/curl
 
 debian-archive-keyring:
     debian,ubuntu: debian-archive-keyring
@@ -295,6 +308,7 @@ gem2deb:
 
 qemu:
     debian,ubuntu: [qemu-user-static, qemubuilder]
+    gentoo: app-emulation/qemu
 
 rubocop:
     gem:
diff --git a/rock.osdeps-python2 b/rock.osdeps-python2
index b7647ab..bedd9d7 100644
--- a/rock.osdeps-python2
+++ b/rock.osdeps-python2
@@ -1,22 +1,27 @@
 cython:
     debian, ubuntu: cython
     opensuse: python-Cython
+    gentoo: dev-lang/cython
 
 python:
     debian,ubuntu: python-dev
     opensuse: python-devel
+    gentoo: dev-lang/python:2.7
 
 python-nose:
     debian,ubuntu: python-nose
     opensuse: python-nose
+    gentoo: dev-python/nose
 
 python-pexpect:
     debian,ubuntu: python-pexpect
     opensuse: python-pexpect
+    gentoo: dev-python/pexpect
 
 python-msgpack:
     debian,ubuntu:
         "16.04,18.04,18.10,19.04,19.10": python-msgpack
         default: nonexistent
     opensuse: python-msgpack
+    gentoo: dev-python/msgpack
 
diff --git a/rock.osdeps-python3 b/rock.osdeps-python3
index 0caf615..065684b 100644
--- a/rock.osdeps-python3
+++ b/rock.osdeps-python3
@@ -1,22 +1,27 @@
 python:
     debian,ubuntu: python3-dev
     opensuse: python3-devel
+    gentoo: ">=dev-lang/python-3"
 
 python-pip:
     debian,ubuntu: python3-pip
     opensuse: python3-pip
+    gentoo: dev-python/pip
 
 python-nose:
     debian,ubuntu: python3-nose
     opensuse: python3-nose
+    gentoo: dev-python/nose
 
 python-pexpect:
     debian,ubuntu: python3-pexpect
     opensuse: python3-pexpect
+    gentoo: dev-python/pexpect
 
 python-msgpack:
     debian,ubuntu: python3-msgpack
     opensuse: python3-msgpack
+    gentoo: dev-python/msgpack
 
 python-distutils:
     debian,ubuntu: python3-distutils
@@ -25,30 +30,37 @@ python-distutils:
 python-setuptools:
     debian,ubuntu: python3-setuptools
     opensuse: python3-setuptools
+    gentoo: dev-python/setuptools
 
 cython:
     debian, ubuntu: cython3
     opensuse: python3-Cython
+    gentoo: dev-python/cython
 
 python3:
     debian,ubuntu: python3-dev
     opensuse: python3-devel
+    gentoo: ">=dev-lang/python-3"
 
 python3-pip:
     debian,ubuntu: python3-pip
     opensuse: python3-pip
+    gentoo: dev-python/pip
 
 python3-nose:
     debian,ubuntu: python3-nose
     opensuse: python3-nose
+    gentoo: dev-python/nose
 
 python3-pexpect:
     debian,ubuntu: python3-pexpect
     opensuse: python3-pexpect
+    gentoo: dev-python/pexpect
 
 python3-msgpack:
     debian,ubuntu: python3-msgpack
     opensuse: python3-msgpack
+    gentoo: dev-python/msgpack
 
 python3-distutils:
     debian,ubuntu: python3-distutils
@@ -57,8 +69,10 @@ python3-distutils:
 python3-setuptools:
     debian,ubuntu: python3-setuptools
     opensuse: python3-setuptools
+    gentoo: dev-python/setuptools
 
 cython3:
     debian, ubuntu: cython3
     opensuse: python3-Cython
+    gentoo: dev-python/cython